Hello,

I have been working on a level design asset for a 2D RPG and I was wondering what would be the best way to push the concept in order to get additional assistance with improving on the idea. I know that a prototype/demo of the level is a good start, and that is what I am working on currently, but with this being just an idea for a dungeon style level what other methods could be used to get others to see my work? 

Do what trailers do. Take only the strongest points of your level design and show them well in your demo. If your level design has one very unique and interesting feature, showing off this feature alone might be enough to get people's interest.

Your title says "selling", your text says "get others to see my work".  Which is it?

If your goal is selling, that isn't going to happen. Nobody wants to buy it.  If you build it into a full game then someone may be interested in publishing the completed game, but they won't buy it.

If your goal is to get others to see it, social media is your friend. If you're looking for eyeballs to review it and give feedback, posts in the appropriate forums here on this site and posts to appropriate forums on sites like Reddit can get some of that.

You said level design asset. By asset do you mean graphic elements for the level? Because when I think of assets I think of graphics. If that is the case, you can seperate all your graphics into their building blocks (platforms, grounds, walls, etc.), and then sell the package on a place like GraphicRiver. People can then design their own levels using your assets.