Hi Romario,
I have been looking at the usual suspects too like RK, Bangbros, Twistys and none of them seem to be doing anything that can be classed as aesthetically pleasing. The best I have come across so far is:
http://www.clubseventeen.com/join
Looks clean but perhaps also looks a little complicated from a surfer perspective.
http://www.18onlygirls.com/
This site has an uncomplicated pre-join page but it isn't anything ground breaking in terms of design.
Makes me wonder why no adult sites that have various price points as well as join options (credit card, debit card, check) don't use join pages like this for example (minus the "what's included"):
https://vwo.com/pricing/
As stated, I totally understand that pretty join pages don't always equate to better join ratios but it just seems that the adult sector isn't even trying to marry the two and instead making other aspects of their sites pretty and letting standards, in terms of design, drop when it comes to the join page.
It's just an observation and I thought I would be able to spark a healthy discussion on the topic.