deviantArt has the "Naruto" problem right now, although there's one group (PoserAddicts - http://poseraddicts.deviantart.com) that gets some good collations out that can get you views and comments from the most surprising of people.

I tend to post in four places, either together or in some combination.  If it's something small, or unremarkable, or doesn't "need" feedback, I'll post it to my blog, and maybe to deviantArt if it's themed towards one of the groups I know visits my deviantArt area (Predator fans mostly), and probably to my Picasa site if I don't mind it getting into the Googleplex Hive Mind.

If I'm really chufed with it (because I learned something spectacularly new in the making of it, or I think it just looks good), or I want peer opinion and/or help with a problem I think is in the final result, I'll post it here and deviantArt,, and hope some kind soul will take pity on my poor untalented behind and help me figure the opronlem out.

If I really get stuck with something, I'm not shy, I'll put it here and send a note to an artist I like/respect/trust and ask if they can spare a few minutes to look it over and give me their thoughts.

I guess it boils down to how you can exploit the facilities you can take advantage of.  But you have to have a thick skin to expose your inner thoughts to strangers, as artists and authors do when they participate on these things.

Here's a thought.  Why not write up a tutorial detailing the steps you took creating that image, the challenges yuou faced and how you overcame them, any tricks you learned, how you decided the skull placement?  You said you don't "do" painting, so this must be something you're really proud of to have done, let people know why and how you did it.

You never know, you might just put up an answer to a problem "everyone" is facing but "no-one" has thought to ask about.