Ahhh....soooo glad you brought up this subject. I was telling my husband the other day that I enjoy taking the pictures more than any part of the whole cookie process.
I was in a magnet program in high school for photography and one of the classes was on food photography (at the time, I thought when in the WORLD will I EVER take pictures of food?!). The obvious part is having good lighting (I always use natural unless if time is an issue) and some sort of texture to the background. I also use scrap booking sheets as they are cheap, easy to access all sorts of patterns, and you can get them with a flat finish (anything with sheen will mess us pictures...my opinion).
I like to use items that will help create some sort of depth for the cookies so they aren't all flat. I don't particularly love flat photos unless if I am only take a picture of one or two cookies...
I did invest in a good camera (I have a Nikon D5100) with a good filter. I used the photo editing software that came with my Nikon. I have always wanted to learn to use Photoshop, but have an issue finding the extra time...on my to-do list lol!
These days, people have such AWESOME camera features on their phones that they don't need to go out and purchase expensive cameras. So...
Anyway, again, I think the photography is the most fun part or all...you get to preserve your little masterpieces forever! 
Make sure to share some of the photo shop techniques once you learn them! I am sure there are zillions of people on here that would love to learn the basics.