This artist has some cute character designs. Feel free to check them out.
Fire; Water; Earth; Wind; Electric; Botanic; Metal; Ice; Force; Psychic; Arcane; Spirit; Light; Dark
There are some other attributes I considered as well, but was unsure whether to use them or not based on if they might have been redundant or because I wanted to avoid using creature characteristics. Here are those:
Crystal; Cosmic; Poison; Insect; Dragon
If you think any of these attributes would be nice to add to the list, feel free to let me know. (note: I can still make insect or dragon monsters without having them as an attribute on the list)