I had some points left over and bought it. The file can easily be extracted from your Steam folder. Would this be considered a paid reward?
Even if it cost real money I'd liken it more to doujins or commercial game official art, but you just buy it with steam points, so I'd assume it would be fine.
I never liked Steelix, heβs so ugly and impractical looking. Insane how you came up with a monster for him, I would hav efully scrapped the idea π