I had practically an entire essay written up on this level, but it came across as very harsh in tone and long winded, so I'll try to compress it down to just this;
Your overworld looks alright, but your first level is filled with design that is clearly confused and directionless. You quote SMB's 1-1 without really seeming to know what makes 1-1 good. Nothing about it stands out in particular, and that is likely the worst aspect of it; it's like playing pulp in video game form. My advice? Skip ahead a beat, build the latter half of world 2, and then come back with a fresh slate for World 1, now with a better idea of what makes your hack unique and what you need to teach the player early on, and approach the player early on as if they truly know nothing about gaming.
You seem to understand level design on some level, maybe not perfectly, but if you make your hack with no unique ideas, visuals, or style like this, your hack will not satisfy you and you'll just end up forgetting it and moving on to another project. Find something unique to YOUR hack, skip ahead and build cool stuff off of it, then teach the player all about how that cool stuff works in world 1.
EDIT: Also, if you're really keen on making this first level first thing, at least watch these videos and try to adapt some of the thought process, rather than just the actual parts of the level itself. Remember that, especially in the first few levels, every obstacle needs to be there for some kind of reason beyond just being a challenge.
1.
Design Club - World 1-1
2.
How Nintendo made Mario's most iconic level
I've become very grumpy these last few years, and have been biting my tongue here in SMWC's forums quite a bit. I just want to let you all know that if ever I come off as harsh, I still care about you all. You guys are great.
(Avatar by
http://reyleias.tumblr.com/, butchered by me)