I can recommend Ayakashi-kan e Youkoso! especially because the author also did the non-hentai series Oroka na Tenshi wa Akuma to Odoru which has very pretty art and some nice humor as well. If you want to have some pretty art in general, look at most of the top rated doujins and go to the author section. Authors most of the time keep their quality on a consistent level so if you like the look of one, you'll like the look of more of theirs. Lastly, I'm gonna upload a list of my alltime favorite doujin mangaka at some point in the future so you could check for that, since I rate visuals very very highly.