1. That appears to be an 8800 model in the picture.
You are looking for another theme. You will be severely limited on themes for the 7290.
3. Our FAQ here has a good third party application list. 3rd Party Application List - BlackBerryFAQ
4. You will find some here that apply to the 7290. Tips and Tricks - BlackBerryFAQ
Good luck, just remember that device is about 4th generation "old" now, and you won't find a lot of support for it. It is a good device, very tough and great for email. It is NOT a multimedia (for lots of pictures, ringtones, etc) device.