No, you can’t just rename .png to .jpg. If you do the SMP will NOT display them. They have to be .jpg’s to begin with, so you wil have to convert Xzeners icons to .jpg. But they will not display with the transparency then. As I said, you can’t use true .pngs with the SMP.
You can use these here which are made for my themes and based on Xzeners icons.
Download them from here: http://www.mediafire.com/?78n7x63qdqjfbu1
Or you can use these here: http://community.wdc.com/t5/WD-TV-Live-Hub-Themes/TW-Genre-Folder-Icons-Updated-6-10-12/td-p/414968
