Good luck. It’s definitely easier just to use one of those colorful skin tones, and search the clothes for older styles and or dirty looking clothes (since they’d be frog monsters) and just describe them to the audience so they can have a mental visual of what the ‘creatures’ look like.
For creation, you could choose to leave off the nose (by choosing the no preview option) and choose the more rounded eyes and bigger lips and a more rounded face? to give it a frog-ish look. 
I’m just full of “this might work” today. LOL