I think it would be incredibly cool (but a lot of extra work) if you made this generate random monsters. So it could select the behaviors, come up with randomized names, and generate images for the user. Then the user would be able to manually modify each one as needed.
For the names, you can do something like this ...
1. have a random list of syllables to choose from, like ba, ca, hu, jo, etc...
2. The program would select a random group of syllables, and stick them together for each monster, so this monster would be the "Bacahujo." You could even have monsters with two or three words in their names ...
Images could be done similarly. Have a selection of different body shapes, head shapes, eye types, mouths, tails, arms, legs etc... Then the program would select one of each type, and stick them together as the image.
A simple implementation of this would be like the old "fashion plates" toys:
https://www.etsy.com/listing/736674057/vintage-1978-tomy-fashion-plates?gpla=1&g...
Where the user can swap out clothing styles for the legs, torso and head. I remember I had a fashion plates that had aliens ... oh just found it!
http://www.muddycolors.com/2015/01/mighty-men-monster-maker/
So you can start with with just three sections like this, head, body, legs, and have just five of each type. Then once it's working, you can add more variety to each section, or add more sections, or both :)
Anyway, these are just some thoughts I had about your project. Good luck with it!
For the record, this is what I have been doing in my game Star Explorers to generate random aliens. These guys have randomly selected eyes, mouths, heads, necks, bodies, tails and legs. They also have a chance to have fur, tentacles and other additional features depending on the environment of the planet...