I would agree with uromastyx's suggestion to ask your current professors and/or current advisors. Naturally (especially if they happen to be in that field), they'll have an awareness of the field and who/where you should be looking at. Also, you could definitely spring for the CAA listing book- it was recently updated, which is nice.
You may also want to take a look at this list for medieval:
I would worry less about the competition/competitiveness, since that's not something anyone applying has any control over whatsoever. I would think specifically about what you want to do and where you want to go. People get accepted all the time into PhD programs without any museum experience, straight from undergrad, having had a different undergrad major, or any number of other things. You're still at least a year out from applying, right?
I agree that you might consider applying to a mix of MA/PhD programs, but I would also advise looking specifically at what seems right for you. Where are you looking to go with your career? There are many board on here which explore the question of "which degree is right for my career path". When I was applying, financial considerations were also pretty important (there are varying levels of funding for MAs and PhDs). Look into schools whose programs are strong in your interests. (Chicago and Brown both have great photo contingents).
First off, I just want to offer you encouragement/good thoughts From what you've written, it seems that you've experienced some success (internships! All those lovely internships!) and some setbacks, but that you've got some goals, committment, and some serious chutzpah. Go get 'em sister/brother/sibling! Honestly, everyone gets rejected, and it sucks the big one. Every single person who is in a program managed to get rejected from a few/lot (I was rejected from 7 schools, some PhD, some Masters). A LOT of people stick with it and do a second/third round of apps (as tortuous as I'm sure tat sounds/truly is). It sounds weird, but you have to know, and understand, that no matter how extraordinary you may be as a candidate, you will get rejected by schools; the hope is, that magically, wonderfully, one (or more!) will accept you. Of course, there are myriad things you can do to try and bring about that magical moment (voodoo comes to mind)- some of which you've already done (classes, German, internships...), and I'm sure there are other suggestions running rampant all over this site.
As for advice (lowly and unqualified to give it as I may be), I can't say that I've ever heard of anyone doing a second bachelors degree (with the exception of the few scholarship programs that send Americans over to Oxbridge for them), and I'm sure there are lots of considerations involved in that (yikes- I could barely afford the first BA!). I have definitely heard of BFA folks doing both Masters and PhDs (roam around this site, and you may find some of those people from previous seasons). Depending on what you're looking to study, there might even be some programs that are more BFA-friendly than others. I'd say, look into things, decide what you want to do- what jobs do you want to pursue, what degree/s do you need to reach those professional goals, what can your budget stand, etc. You may want to consider applying to a mix of programs/program types (MA, PhD, art history/museum studies/curatorial stuff/American studies) to find things that work for you more perfectly (more perfect for you, higher chances that you're perfect for them...theoretically).
All the best of luck! Defnitely look around this site (cue robust search feature) for people in previous years who have had similar backgrounds and who have sought out similar advice!
There's always the option of taking a paper you wrote during your undergrad, and using that to spin off into a more in-depth look at that topic. If you have a paper from undergrad lying around that you don't hate/still feel a bit connected with, you can consider expanding and refining it into your writing sample. That way you're not starting from scratch. I would still advise asking a professor or two that you feel comfortable with to look it over.
Strange suggestion- but have you talked at all with Robert St. George at UPenn? He's technically in the history department these days (he's also been appointed in the Art History and Folklore departments), but your interests seem to align very closely with his. Also, he's just about the nicest person I've ever met, and if you're interested in getting to know people, I imagine he'd be very willing to chat with you- departments, general advice, zany ideas, introductions to people, anything.
I'm going to agree with fullofpink's comments in general, but also specifically second the suggestion that you ask which piece of writing the school you're appling to would like. If you feel comfortable contacting someone in that department (or if you've been in contact/met with someone in the department), it shouldn't hurt to ask what they think or what they would like to see from you for your writing sample.
I'm also going to second losemygrip in regards to not selling yourself short competitiveness-wise. If you absolutely know that the Ph.D. is what you want, then don't let other people's percieved competition stop you from applying for those programs.
Agh, I'm having such struggles trying to secure a place. I had an apartment I loved, but the lady called me today and said I didn't get it and there were no other available units in the building So, now I'm eating my weight in discounted Easter chocolate and trying to resign myself to finding another "perfect" place. The thing is, it's almost impossible for me to travel up there (almost 6 hours by car or train), especially because I'm right in the thick of final papers (and spent all my travel money on discounted Easter chocolate ) Blargh. I'm having a heck of a time trying to convince these real eastate people to talk to me. Yeah, I'd love to come tour your apartment, but I can't just come see it, and by the time I can go see it, you'll have already rented it. Some incredulous agent just told me to have a friend look at it for me (I don't have any friends north of Pennsylvania, but thanks?) Struggles. Thanks for letting my rant guys.
What have you been searching for? Try "east side"- if you haven't already there's also some more specific neighborhood names, try using those? Or look for major street names (Thayer, Hope, wickenden).
Apparently there's also a lively listserv among the grad students that you can sign up for once you've gotten a brown email address.
Best bet now is to get in contact with grad students in your program- they have the best suggestions!
Doesn't seem necessary to buy a house, in my opinion (then again, I'm not financially in a place where I could buy a house anyways.) from what I saw, there are a lot of options well below $1000. I'm aiming for a studio or 1bedroom at around 800. I wa told by some grad students that rents are very area particular- prices drop just a few blocks off campus (this is where all the undergrads live apparently, and they're not great apartments anyways- very depressingly run down on the inside.) if you go north about a mile, it's a very popular spot for grad students and reasonably priced. If you plan on sharing with someone, it is even more cost effective.
Alrighty- I've got the low down on housing at Brown from my visit. Two "spines" of campus= Benefit St. and Hope St. Major Neighborhoods= Wayland Square, Wickenden, Ives (which is aparrently sketchy), sort of north of campus (although I was told there are some "sketchy" areas up there, so I was instructed to "go investigate" before renting up there). I really like Benefit- it's so pretty and historic and ridiculously close to the Amtrak station/recently nice-ified river/important campus buildings for me! I'm looking at apartments tomorrow!