dude, i love your project (i really do. the gameplay is fantastic) and all but the visuals hurt my eyes. want some advice? get an art director. if you have some money left over, i could put you to the right person (no, not me) who knows all that you need. he wont doit for free of course.
but ill do a few things for free. first, your graphicsl style neesd to fit the game. make it cartoony or cgi-y, much like mario galaxy or zelda wind waker. you can combine that with a simple yet effective style. when i take a look at your player model, i see simple round shapes. so id say go with that theme for the whole game. simple round shapes are easy to produce and look great if youre doing it right. use cartoony textures, with alot of round thingys and alot of colors.
create nice backgrounds for your levels, not just a dark cave. a cave can be made with color aswell.
like this:
http://www.pinkpt.com/neodex/images/5/50/Fungus_Cave.gifor that:
http://www.bluebison.net/backgrounds/2007/1107/bats-in-a-cave-with-waterfalls-1600.jpgit has little color but it has alot of details. something along those lines. use paralax scrolling to enhance the effect.
then get some quirky music and SFX to add some mood. i could help you with that if you want.
be creative. play a few modern side scrolling games like the freeware "legend of princess" or the new "Dragon Ball" Game for wii.
have a few examples:
http://wiimedia.ign.com/wii/image/article/959/959158/a-boy-and-his-blob-20090304101116560_640w.jpghttp://quiksave.net/wp-content/uploads/2008/05/emag_lostwinds_041508_5_47695.jpgi personally prefer 2D backgrounds and stuff but thats up to you. you can mix them, thats what id do but its your game...
just my two cents
