Keep in mind that SRB2 has a start and an end. Between the start and the end, the player must accomplish certain tasks to get to a finish. Basic tasks include jumping and locating how to procede in the level, although other times they might be a bit more complicated. Such examples would be killing all of the enemies in a room, or running through a corridor that has crushers in it.
Your level seems to really be lacking some intersting tasks between you and the finish. Raising a few sections of the land so that the player has to jump onto or over them could definately add some more interesting gameplay to your level. As you get better at level designing, you'll be able to make more interesting tasks that make a better final product.
Oh, and don't forget: Making levels pretty also makes them more interesting to play, even if it doesn't actually enrich the gameplay any. ;)
