Album Art on M6 SL

My first question is does the M6 SL even support album art?

Second: What size, format, etc. does the album art have to be to work on the M6 SL (if it is supported)?

It is supported. Put a jpg file in your album's folder and name it as the album's name (id3 tag). 100x100pix images will work if I remember correctly.