Certain palettes and specific species/themes for sure for me. 

Any black/grey characters catches my eye or any water themed creature. I'm also a fan of simple shaped critters, things I can draw without so much stress about perfect anatomy, seals are a good example of this 

i really like detailed designs! i tend towards sparkledogs for that reason, if you want the character to be more simple you can always just take a marking or two away instead of having to totally change the design!!

and also darker/edgier palettes and goth/emo/horror theming bc 90% of the adopts i see are either pastel/pastel "goth" or all beige and green, like that really muted cottagecore shit.... not a huge fan of those