What needs to be done:
-Flowing water/lava -Ehh....
-Sounds - Yes. I have all sorts of instruments. Bad quality recording - if you have something to fix sound. Or I could get my awesome video recorder.
-Choose from Tiny/Small/Normal/Huge map sizes - Oof. I'll think about it.
-Multiplayer (Unlikely) -No experience whatsoever, although I do have a friend who is experienced in it, and DOES have a multiplayer game. It's in alpha, only me and him and shelton and someone else even KNOW of the site. He knows how to work Multiplayer. It's called The Tenements, if you're interested. (not released to public) You'll have to be willing to let go of some money for multiplayer for a multiplayer server host, is what he told me.
-Map saving/loading - Possible.
-Particles when deleting blocks -Erm..
-Skins (Unlikely) - NO clue.
-Map generation (With different themes, like: Hell, Snowland, Mountain) -Explain, please. at my first thought: yes. Want to make sure.
-Make Sand and Gravel fall down -physics, hun. Set gravity. I can do this.
-Change block slot from block bar by using the mouse wheel - Might be able to, depending on your coding.
AHEM. Not to drive anyone away, but i scanned this with my anti virus and it said it found a threat. It could have been wrong; I'll check again. + + = World's fastest shovel that doesn't run on electricity =)
I yet to see a 2D minecraft that could impress me well it's just the fact that so many owners just give up. A 2D minecraft has a lot of potential to become very good but the owners slack off and don't try to much. I'd actually play a 2D minecraft that's actually good and like the 3D version a lot! But sadly there is no such version that meets my standards.