Personally I'd like to see things like Tabula, Tangerine, Heartbreaker, Scorpio battleground or even Bluebend, Archer's valley and rysia, but I understand that they're all probably considered too metal heavy.
AquariusCrossing and Terra are probably small and low-econ enough and also look like they'd add quite a bit of variety to the matchmaking map pool. For comet type maps I'd suggest green comet.