Dude your art is fracking gorgeous. Give the forums a shoutout when you publish, because I will be there.
(Its funny too - I was just going to say most of the comics I follow on Tapastic are the ones made by or suggested by forum peeps. Although I will say if I'm at the front end of Tapastic I go by A - icons sell it for me.)
No worries, I get just as if not more crazy when it comes to variations in my artwork. I had my own comic vetted by the tapastic community here and they gave great advice (And I gave them like a bajillion variations to look at, so seriously, thanks guys!). I love all of your versions as illustrations, so definitely hold on to them for promotional material or for your blog.
I will say the bottom most probably works best as an icon, and maybe the top most also - if you make the background completely white (its like a very light grey). The reason is, the white blends into the white background, so yours stands out as an interesting shape while everyone else just has these colorful squares. The way even the skin is kind of white and blends into the negative space looks really cool.
Here was my first thumbnail - before my characters got introduced - for my webcomic Knights.
For my current one, I pulled out art from a panel I really thought I'd done well and made some variations, eventually settling on this:
