A while back I set aside some time to create some new thumbnails for use with general and placeholder posts and entries on my various art sites. I might make more in future, but they took a fair bit of time to make and this set covers my bases fairly well.
In order, here's what they're mainly meant to be used for. I kept them a little generic for flexibility's sake, but this'll explain where I was starting from.
Open for commissions notifications - this is for my commiss.io page to make it very clear when my queues are open for whoever decides to check the page directly
Noticeboard - general news, updates, notification posts etc
Poll clipboard - pretty much self explanatory
Sketch paper - concept art posts or YCH slots for the YCH section of the site; namely ideas that can be bought but which don't have any premade artwork to show for it
Diary - journal posts, also fairly self explanatory
Closed for commissions - same as the open notification, but for when I'm closed.