Firstly, when you submit your level to the contest, do not submit it as a .ips patch.
Instead, download Floating IPS from the tools section here to make a .bps
patch. (You can do more research yourself on why .bps is better)
As for the level itself, I think this is pretty good for your first time! A lot of people starting out try to put whatever wherever, but you have a clear theme and limit yourself to only enemies that you needed.
There was one group of 3 koopas and a piranha plant that seemed kind of awkward, since there were so many enemies in one spot.
Overall, my main complaint would be that it's almost too easy. One of the joys of Mario is thinking fast and being light on your feet, while the main challenge in this level is timing your jumps.
Also, even if you're not sure you're ready for graphics stuff, try the palette editor at least! It's amazing how different colours affect the overall feel of your level.