Going through his galleries, it seems that his most recent work maintains some fantasy motifs (along with alot of sci-fi, intrigue and lite bodice-rippers), mostly executed through photomontage and what looks like some use of 3D rendering software. Scouring the internet, I came across some other images; it seems Stinson did a good number of book covers, including the cover of Jerry Weissman's The Zodiac Killer (for some reason this has the most image hits if you Google image search Stinson's name).
It's worth noting that no where in the documentation for The Wizard and the Princess is Stinson's name mentioned. It's also hard to say if he illustrated the other black box Hi-Res releases--there's plausible stylistic similarity in the covers to Mystery House, Cranston Manor, Mission Asteroid, and Time Zone (Ulysses was clearly not done by Stinson), but I'm not versed enough in illustration analysis to say with any certainty. Some of the full-color multi-page Sierra ads I've found in 1982 issues of Softalk also utilize the artwork from these black box covers. As Raiford Guins notes in his forthcoming book Game After, most illustrators of game box art and arcade cabinetry toiled in total obscurity, despite the profound mark their work has left on our memories. This little digression through the realm of illustration history also re-affirms how much work there is to do in game history on things "beyond the game" as I like to say.
Unfortunately, the email address listed on Stinson's website is defunct. If anyone knows anything more about Stinson, or anyone who work on illustration and cover art at Sierra On-Line, please drop me a note!