I'm iffy about the water. You can only "swim" if there is resistance from the water. Because toribash objects do not provide a resistance, there would be no way to move. Imagine setting the gravity to 0 and you're in the air. There's no way to move unless you push off the ground or objects, the case would be the same with water.
About the images, I think this has been suggested, and I like the idea. However, I think it would be best if the images came stock with each update. I mean, if you were making a mod, you could have the new cube/block as "brick" or cement, or whatever. I like the idea that people can upload their own pictures, but I feel like there would be that one person who releases a mod that puts a bunch of penises on the walls lol.