dump time

[Akira]

That is a horribly awkward way to push. Have you looked at any references? There are thousands of skate videos on youtube.

[hsn2555]

cool ones !
about your guy,the board seems to be too huge for your guy,and the stance he's taking on the skateboard is not correct,if you're aiming to keep it going fast it's supposed to look like this :

as well as the push,

[Keith]

I thought the cape was some sort of jet exhaust system. I'd suggest clarifying that by making the cape not move quite as much or not so bright where it connects to the character. Plus the cape is distracting my attention away from the character.

[Reo]

I thought the cape was some sort of jet exhaust system. I'd suggest clarifying that by making the cape not move quite as much or not so bright where it connects to the character.

or/and give it dark outlines like the rest of the sprite.

[Tuna Unleashed]

keith/reo- that's how it is in viewtiful joe. look it up.
akira- unfortunately all of them are of tricks, none show any pushing.

[willfaulds]

keith/reo- that's how it is in viewtiful joe. look it up.

no reason for you to not try and improve things...

[ndchristie]

http://www.wonderhowto.com/how-to/video/how-to-learn-the-basics-of-skateboarding-276671/

12 seconds of searching and there's a dozen others that show all about pushoff and kicking on the first page of results.

[Tuna Unleashed]

the arm movement needs work
edit:

[Gil]

It looks really unconvincing as far as skateboarding goes, you're better off completely redoing the animation and finding a good reference. I don't think you will achieve a proper result by further finetuning of this one. The proper keyframes are just not there.

[Rox]

Yes, the biggest issue I have with the skateboard push is that people don't stand sideways while pushing. A proper skateboard push would have some frames in it that look very similar to a run animation. Something sort of like this. Imagine ... I don't know, image standing on a towel on the floor and pushing yourself forward with the other foot, or something, and try to observe the orientation of your body. While actively pushing forward, you're going to end up completely facing the direction you're trying to go.