If you couldn’t find anything when you read the rules, it would be safe to assume you’re good to go…
To be perfectly honest with you, $1 feels a bit steep for what’s on offer. Just from what I’ve seen while browsing the Release Announcements I would say that three more characters/enemies should be included at that price. Don’t forget: Your character probably won’t fit in with other artist’s art style. Offering a whole set would give potential customers more motivation to make a purchase.
And please consider adding the license you’re selling the pack under via the “Metadata” tab of your project page - so customers know how to handle it. There was a case recently where somebody bought an asset pack and basically re-sold it (with very little changes) - presumably because they were too lazy to check what copyright is… You do not want to deal with that kind of stuff.
[Edit:] Just to clarify: I’m not suggesting that your art wasn’t looking good - I’m just saying that it might be hard to work with the amount that’s on offer (which would be true regardless of your pricing).