Hello!!! I have experience here. A few years ago I sent a weather balloon into sub space also and captured some beautiful pictures of the earth. Here is one of them: http://flic.kr/p/fU77w5
Sadly, the imagery didn't quite turn out as expected, it was a little blurry but it was still breathtaking. I strongly encourage you to take pictures. The camera that I used was a nikon coolpix s500 I think.... With that camera you were able to take pictures every certain amount of time. If the camera that you use has a focus option, set it to infinity. Also, use a Styrofoam cooler to house your batteries, camera, and arduino. Get a fairly big one so you can find it when it touches down. Paint it orange so that you can see it. Put hand warmers inside to keep it warm. Launch early in the morning so that you don't have to deal with wind while inflating your balloon. Use a spot tracker or similar satellite tracker to transmit the cooler's location to you upon touchdown. Launch on a day when the jet stream isn't above you. If it is (mine was) it will travel 200+ miles from you. Attach a parachute to your string (should be 100 ft long) about 2/3rds of the way up. Make sure you zip tie your cooler shut, and above all, have fun!!!