Just checked out Tumblr for this first time; I don't get it. I typed in ninja turtles and got related images. How's this any different from a google search?
You've got safe search on I imagine. The more blogs you follow or the more "down the rabbit hole" you go by typing certain tags, the more you'll see. Tumblr is full of slash-fics, slash-art, everything! The most notable examples are Stucky, Stony, Superfamily and all that. Thing is, the Stony tag bleeds into the Iron Man tag. The FrostIron one does so as well. And instead of looking at Iron Man art, you're seeing Loki and Stark do the nasty in many different and "exciting" ways. It's annoying to say the least. Even if you have safe-search turned on to avoid that, the fan-fics and the "Outrages" are there to clutter the board. It takes a while to create a truly great Tumblr experience.