Tip: If your level contains elements that temporarily change the music to a global song (such as a P-Switch or a Star), that music will not stop playing after the intended end time if the music bypass setting is set to 00.
I'm not too fond of your drawing style usually (my opinion, no offense), but I have to say that background looks really nice. I especially like how realistic and detailed the clouds look. It could be a bit hard to tell apart the platforms in the BG from those in the FG. Might just be the screenshot though, it'll probably be easier to tell in-game.
Looks pretty nice - correct perspective, a fair amount of decorations and few graphical glitches. The only real flaw I can find are the missing corner tiles (see the picture below). Also, you migth want to try adding other types of curves and creating a custom palette to make your overworld look more interesting.
Location: Joinville SC Brazil
@ The Heavenly Haunter: That level looks really good, but I do agree with Mario616; some of the sprites do clash a little bit with the palette, but at the same time, I really like the volcano palette, so I say if you do change it at all, make it just a tad brighter, but not much.
Also, the background animates? I'd really like to see that in action.
@ Mario616: For just being an alpha OW, I actually like it a lot. I'm not sure about Bowser's castle being in an ice world though; it just seems out of place for some reason.
There's also way too many levels between those two castles on the main grassland (in my opinion) - perhaps a fortress somewhere in the middle or something would help break the world up a bit.
Partly to add some.. extra oddness to my hack. It looks and sparkles like a goal sphere, but when you approach it, it shakes and then jumps into A WALKING GOAL SPHERE SPIDER. You have to jump on it to stun it for a bit, and then throw a brown block at it to insure damage. After hitting it for a while, it turns into an actual goal sphere, allowing you to beat the level.
Not to mention this was inspired and made for Halloween.