1. What’s the optimal size for the folder.jpg icon. I’ve seen some done at 200x300 and 192x369px ?
200x300 will be fine (experiment if you like, to compare image quality at higher or lower resolutions)
2. Do they have to be jpg files (i.e. with a filled background), or will the SMB support tranparent .png files for Icons ?
Yes (the SMP does not support alpha transparency .png files [only the Live Hub does, Firmware 2.07.17 or lower] )
3. Is there a good resorce for looking at some folder genre icons (to get some ideas) ?
here’s a start : http://community.wd.com/t5/WD-TV-Live-Hub-Themes/Movie-Genre-Thumbs-plus-link-to-others/td-p/562337
