Screen names are like billboard headlines, which invite others to at least check out the product.
Online, I've found that the more abstract the screen name, the more guys will message me and ask questions, which ultimately leads to a conversation- the best way to assess a match.
Rest assured, you don't need to come up with an award-winning screen name to attract attention.
Often times I use a favorite song title or a word from my favorite movie- something that will spark interest or prompt other hopeless romantics to look at my profile.
Even if you can visualize your ideal mate in your head, it's a good idea to draw him on paper.