Hi, I really like what you have right now. Its not so much a mess but something I think can be improved on, that is with more reference to the comic in terms of the colour use and tiles. I'm not sure you should go the generic platformer tiles with this game mockup. I'd stick clear from it in fact and try as best as can to stay as close to the comics style. If your new to pixel art or art in general then Its not a problem I'd carry on with the route your on now.
I actually did like the original mockup more, it was clean in terms of style, just like the comic. but had a few flaws as Facet has pointed out.
I'd actually look at this image, it seems more feasible as a reference.
http://potatofarmgirl.deviantart.com/gallery/#/d35q709The character is also missing some characteristics, such as the tuft of hair on the back and in front of the ears. The hat(I think its a hat) looks very flat and I think that selective outlining would work very well with this character. You are also missing a lot of darker blues, which are used for selective outlining and general shading , and your colours are very close at times, so it can be very hard at times to read the detail that you've so carefully placed. I'd urge you to create more contrast.
Are you working with a limited pallet? If you'd like I could do a edit of the character. Oh and sorry if I'm being vague, I'm not good at putting into words what I'm thinkning and working at a pub and having 3 shots of Vodka isn't helping