It looks pretty good for on an iPad (I do mine on an iDevice too :D). My only suggestion is to make all the colors clearer and less smudged together. You can definitely still get cartoon style (which below seems like what you want).  Just stick with it until one day you wake up and figure out how to do everything perfect.

From what I can tell you're using a airbrush tool on all of these. I'm not dissing on the airbrush tool or anything but a regular brush would be better to define the lines more. Also spend more time on your drawings, 5 minutes is hardly enough time to be spending on any drawing.

Errrrr.... no offense, but these are blurry, fuzz together, look like they were drawn by a toddler with crayons and if you hadn't told me what these were i wouldn't have guessed. depending on what program you used to create these, try making the brush harder, use lines first on a new layer (as many drawing programs use layers on iPad) and please please please only post the better stuff

And in case you think this is a hate comment, here is TNT with 500x500 Pixels:
http://i1358.photobucket.com/albums/q769/1likecheese/proving-you-wrong_zpscca5f1ee.png

So not hd! But pretty good...