If "Sandrateen Mod" suggests it's part of a game modification (mod), it could be a graphical asset, a bonus level, or part of a storyline within the mod.
(DDLC) or other visual novels, "Fan Packs" or "Bonus" files often include high-resolution artwork, wallpapers, or concept sketches. Asset Categorization Sandrateen Mod Bonus 009 -11- jpg
: