A basketball court seems to be the most expressive canvas for designing, it seems, and gridiron football is second behind it. It makes it almost suck to be a GM of a team in Furry League Baseball. Not many places to put your logos on the baseball diamond. There you have only foul territory, either behind the home plate circle, between home and first base, or between home and third base. Nobody seems to want to mess with the area between the foul lines.

I agree, though I've seen ways grounds crews in baseball have gotten artistic, often with how they cut the infield "diamond" as well as the mowing patterns of the turf (especially during All-Star Games). I've also seen how many teams will paint the logo right behind home plate, and on several college fields (as well as Fenway Park), they tend to have a strip of astroturf behind home plate, which they often use as an extra canvas.

That's why you see all the work done on the outfield wall itself and some of the areas around the stands and the like. I'd say that is where baseball tends to be more expressive than most sport, the building, scoreboard, and walls themselves.