Dark, mostly. I really like and appreciate a clean theme with limited/focus colour palette. And keeping readability and accessibility in mind. But I'm also a fan of unique takes using graphics to create an entire scene, but nothing cluttered. One example would be nature, earthy, wood inspired themes . Beautiful, if done right.
I like vibrant colors! mine's super dull right now, doesn't help that idk css so its pretty ugly, but i really like vibrant saturated pages
I like darker colors similar to your theme. Mine is just black and white right now because I haven’t gotten around to coding a proper theme but I love themes with creative color combinations as long as they’re easy on the eyes !!
im a big fan of cool and/or darker color themes tbh! bonus that theyre a lot easier for me to look at...
also a readable font for the main text sections (questions and answers, posts and the like) is also nice! like for the motivational header above the box to ask a question, i use a more cursive font but i use a more readable font (at least for me personally) for the rest... it just so happens to look like the font used in persona 5 royal too LOL idk if my font is currently working though...
readability, legible fonts, not too bright.
Anything w/ a dark background. Pure white hurts my eyes.
COLORS I LOVE COLORS (but if a profile is very light and text isnt easy to read its a no for me......) also css looks good when done right but ive seen it done over the top before and it feels like im entering another dimension (i ahve css on my profile but currently its only to hide the neospring logo, hide my followers/following, and to give the gradient for the top nav bar)
Readability!! I need a theme to have good contrast, no light on light or dark on dark. I also want fonts to be readable! I use a fancy script font for my UI bc it's pretty but for things like posts and questions and answers I use a different font that's easy for me to read. (Bonus that it's the official Genshin Impact font)
Had to think about this for a bit before answering my own question lmao, but what appeals to me most would probably be the colours, I've been here since way before the css update so it was the most we had to work with. In my opinion, as long as the colours look good, even if you have very simple/little or no css your profile will look good