Superheroes need foes! To be honest there isn't much point in being a superhero unless there's someone or something to fight. Often, it will be someone else who likes spandex costumes and has superpowers only they like to use them for evil, not good: a supervillain, in other words. But what else might you fight...
How about all the fantasy monsters that many of you know and love from fantasy, swords and sorcery RPGs?
Here the good folks at Rogue Genius Games have made a start at a systematic retooling of monsters from Dungeons & Dragons 3X (under the OGL) to Mutants & Masterminds 3e. They are not the only people doing this, from inhabitants of various online communities to other game publishers, but this is the first systematic bestiary (rather than a handful of monsters selected for a specific purpose) that I've seen.
The approach is systematic too, with each beastie getting a full stat block as well as descriptive text and sometimes an illustration. The descriptions are quite concise: if you need more, consult the 'fluff' element of the original, modifying it as necessary to suit the campaign world that you are using for your superhero game.
Not every creature gets an illustration, but the ones here are fresh and new, and in an appropriate comic-book style.
This is an interesting innovation. It won't suit everyone's superhero game, but many creatures can be used as 'aliens' (or their pets) if you have alien invasions as a theme in your game, whilst some may have developed under the influences of the same forces that have caused some individuals to develop superpowers in your world.