Looks Good
The art looks good. I havent seen the movie though. They seem to have sort of a childish figure if you ask me. It portrays both their inner childhood yet the seriousness of the situation. The background looks REALLY good. The only problems I see are the good looks a little too....boxed? That, and Spike's waist should be a little lower.
You could try some hentai. Im a fan of the stuff, but only if it's good. This looks pretty good, so go ahead. Give it a shot.