Well, I think a "liquid" texture is needed, even using it with the multi shape blocks.
A texture of the same type of the water in the game (texture that actually moves) could be great.
Would be great have the ability for painting that textures, for emulate blood, milk, honey, etc, etc; and the opacity of that colored texture.
Red51 has said before he plans on adding water blocks, good ideas on the painting / opacity part of it.
Another texture I really want to see on the game (but I don't know if it's possible for reasons of performance) and forget to mention it to red51 before:
MIRRORS
Please...
Unity is capable of doing mirrors, but unless they've changed it it's basically creating another camera inside the game that then displays that on the mirror surface. Only having a couple isn't too bad, but the more you have then yes it does impact performance rather quickly. That's why most games cheat a mirror effect and you usually only get this blurry shadow projected on a mirror like surface.