Advertising help

so i'm running a server called seacow, and very few people are joining. most people who do join really like it, and very few don't. so i'm assuming that there's not much wrong with my server, i'm just not advertising it right. payed advertising is not an option. does anyone know any good websites to ad your servers for free? I've already posted mine on pmc and MC server list. how do i get people to join my server?
check the server out yourself: 66.130.242.246:25555