Photos are just one part of a professional dancers promotional package.
My best suggestion is to book a photo shoot at least twice a year. Put it on your calendar and make it happen! Promoters and anyone that would consider hiring you like to look at fresh pictures.
If you can't afford a professional shoot, find a friend with a camera, set up a backdrop with some good lighting and go for it. Post an ad at the local college for a photography student to take your photos. They will usually do it for free because they need it for their portfolio.
The best backdrop to use is white with no texture. It's a lot easier to punch your photo out of the background in photoshop. If you are wearing a white costume use a medium color backdrop. No texture is best for all photos. If you don't have a white backdrop, at least use a light color.
Do a photo shoot party with some of your belly dancer friends in your city. Invite some dancers you don't know very well. Great way to make new friends and its a lot of fun.
Don't forget your complete belly dancer look: hair, makeup, costume and maybe some jewelry.
This also reminds me of a funny story. One of my friends and I came up with the 30 Year/ 30 Pound Rule. Sometimes you'll see what is obviously an older picture of a belly dancer in a magazine ad or elsewhere and one of us will say: They're in violation of the 30 year/30 pound rule! Write 'em a ticket!
Don't get me wrong, we love the classic photos, BUT we would love to see new, hot photos of you! Everyone ages and some of us get a little chunkier - please don't let this stop you from taking new promo photos. You won't regret it.
I look forward to seeing your new photos.
PS - Remember,,, every six months. Just book it!