Thanks to the new online level searching methods any level i reference here you can search by title for and play for yourself! If you are looking to play a level with the paint-gun then search for newest created levels, usually things churning out now days have the paintgun in it. If that doesn't work look through the busiest levels, and if that doesn't work, look for a MGS looking level, or any level that may have a shoting premise. Even levels without shooting implied end up having the paint gun thrown in somewhere.
Anyways, here are some levels you should look up and play. They all demonstrate good themed levels that include the paintgun, and keep a balanced sort of gameplay that doesn't just use MGS enemies as their bad guys.
The first one I stumbled upon was called The Human Body! Its a fantastic level where you start in a hospital and soon after a doctor shrinks you and injects you into the sick person. You are given a paint gun to kill the evil virus and germs! Its quite a laugh and theres also small puzzles where you have to put down the paint gun, and grab stuff, something that was missing from a lot of early MGS DLC levels.
Nightlife was another well rounded level that made me enjoy myself quite a bit. There are just so many levels out there now that are so good, its amazing that all this content came from other users. The littlebig matrix was even fun, obviously the title implies the paint-gun, which is just something you have to look out for if you want to play be playing around with the paintgun. Another good series to look for is the MGS missions by X-nobody-x. He has about 9 missions that are directly related to MGS, and they are all quite well done.
In the end though the gameplay has only changed slightly, but in that slight change many ideas have sprung from it, and created a broader experience inside the online community of little big planet, whether or not you purchased the DLC! There are still classic game levels being created without the DLC, for example the wizard of odd was very good.
So get out there and look for levels to share and play, and for god sakes people... keep creating! You are making this game worth playing!