[WPTouch] HOW to remove Post Thumbnail mirror shadow ?

Any way to remove the “mirror shadow” at the bottom of each round-corner 50 x 50 Post Thumbnail icon?

Also when the featured image in my post is not 50 x 50, I found that the image in the Post Thumbnail would get deformed (it might be better if it crop the image instead of deform the image), anyway I could do that ?