I like the "Fully Connected Map" mod, and the upcoming "Donut Mod" with custom Level 4 map.
I'd like to see a mod based on The Simpsons Movie, with an entirely custom Springfield map that's trapped in the Dome.
Notable features would include:
Having the Simpsons House at the edge of the Dome with the Maggie's Sandbox Sinkhole reference.
Frink's drill just outside the Dome.
Springfield Gorge (Reusing the Gorge from Road Rage would be acceptable).
The KBBL Tower used to reach the Rope to escape the Dome.
The Church and Moe's Tavern being next to each other.
Most of Springfield will be in disarray except for the School.
The Russ Cargill Screen projection on the Dome.
Lake Springfield with the Blockade and Picket Signs.
Lard Lads shut down by the health inspector.
A interior for Krusty Burger, with a censored Bart stuck to the outside of the window.
And any other reference that would work for this Trappuccino Mod.
I'd make this mod myself if I could have the patience to learn how to make map mods for this game.