Many rare or largely forgotten picture formats (including .abs and .skf formats) can be usually converted with the use of some of the dedicated picture conversion programs, because these programs usually support hundreds various picture formats and might also allow abs to skf conversion.
However, it would be probably wiser to use some of the more common pictures like JPEGs or PNGs unless you really need some of the uncommon picture formats.
Updated: October 20, 2022