Hmm what I would suggest you is to add renders some pictures with blank material with full resolution : it will be quicker than with textures and transparency, will increase your score and you can place these just after the first preview picture ;)
Also expand description a bit.
For the price I guess that's a good one, not gonna lie these times it's hard to sell I don't usually sell more than 15$ models but you can try at least ;)
Goodluck