I'm looking for specific websites that focus solely on this.

Thanks!

you want to be on a book cover?
hmmmm,... thats a tricky one. i dont know if theres a website just for that.
Theres a lot of odds there.
First you'd need representation; management / agency or some otherwise strong presence.
Then you'd have to hope someone is writing a romance novel and in that book theres a main character that you could resemble and the author would want that character to appear on the cover.
Then the author would have to task the publisher with finding someone to cast for that cover model, and that someone (the artist or photog most likely) would have to find you by contacting whatever entity represents you.
and that all needs to take place somewhere local to you, because theyre probably not going to have a huge travel budget.

soooooo.......

Perhaps your best bet is to sort of reverse engineer this and make it happen!
contact some authors and publishers of such books and send them your comp card and let them know your goal of being on a cover.

or maybe start working with well known photographers taking the kind of images that end up on romance novel covers and hope one of those images gets you there.

the above advice is based off the only personal experience i have with this sort of thing;
some publisher contacted an agency model i had photographed and asked her if they could use an image they'd seen of her for a book cover.
she contacted me for permission since i had taken the photo, and i signed off the paperwork and stuff.
it was just a shot i took of her sitting on my couch. it wasnt anything we ever thought would end up on a book,
the entire thing was just chance.


good luck!