ACEOs

I'm brand new to the world of ACEOs, and as a matter of fact I never heard of them before I opened up my Etsy shop, but I'm finding now that it's kind of cool to create little mini artworks. People tell me that they're very popular, though I don't know just yet because none of mine are sold. So if you're a collector of the ACEO, please let me hear from you! What do you like to see? What subject matter, what media? I'd love to know... and besides that I could use a few ideas. I'm walking in the dark here folks!