Contrast tank:
Might have a bit of trouble selecting many types of fish, but would look neat, albino fish freak me out tbh.
Brackish:
Would be lovely but you don't have a lot of options. Marine?
Goldfish!:
Neat, but you couldn't keep many, just 2 fancies!
Cichlids:
Good, but you wouldn't be able to keep a lot of the bigger more colorful species e.g. mbuna.
Invertibrates:
Would be interesting, like the idea, but how about some rasboras to occupy mid-upper levels? Would be sort of boring without. Love the idea of planted w/ inverts and maybe some harlequins above.
Neon tetra:
Not a fan of them.
Plants:
See inverts. Love planted tanks, but why just plants?
Clear:
Not a lot of options, but interesting.
Specialty:
Could be interesting.
Betta:
You could do a sorority of about 20 females easily, would love this idea! I think you could get away making a planted tank w/ decorations like that of a thai rice paddie - place. Lots of mosses, etc, think it would look fantastic, also you could add some cories and get away with maybe 15 females. Favorite option IMHO.
Underwater city:
Meh, not a big fan of it.
o.0:
Odd fish like blind cave tetras (no eyes) weird catfishes etc? Or planted biotypes like the amazon, asia
Color Specific:
Blah... boring...
Reverse contrast:
Dunno.
Elephant nose:
Don't know anything about them.