For me, it depends how thick! There are hot babes that are thick and there are others that ... you better avoid them. /r/Thick is all about girls that are thick, as you already understood from my first line. It doesn't allow porn or sex - just submissions of babes with huge asses, shapely tits and good proportions. Note that Thick isn't a place where those fat feminists are gonna find material that endorses their love of cake - the girls here aren't really chubby, but perfectly proportioned for your viewing pleasure.
The guys like big asses, but thick thighs have also made quite the impression as of late - it's a real mixed bag. I think the best way to describe it is if you took /r/Skinny and /r/Thick and combined the two, you'd get what many would consider to be a 'normal' chick. Eh, but what do I know?
The subreddit has 72,000 readers and new submissions are made about ten times a day. You're welcome to head on over there and offer your own material as well - the community is all about you showing what you think is perfect when it comes to the niche of thick chicks.