If you have a non-square or rectangle image with a transparent PNG background, it will show up as not transparent.

Here’s my technical assessment: What’s up with that?

I suppose WOO has their reasons, but if you want it gone, the code is below. The images speak for themselves. Hope this saved you some searching and frustration.

What's up with the non-transparency?

What’s up with the non-transparency?

Ah, that's better.

Ah, that’s better.

[divider] 
.entry img, img.thumbnail { background:none; border: 0px;}