devtrackers.gg
PHXL has said in the past they are unwilling to do anything of the sort due to the legal hurdles involved in implementing such cosmetics.
Also, there's a chance the perception would be "PHX is outsourcing work from its fans for free" and we really don't want to do that. It's a fun idea, but has a ton of hurdles, unfortunately.
I'm currently wondering if a live stream with a concept artist would be a fun middle ground. Players get to throw suggestions in the chat and watch us bring them to life.