>>11188688here are my suggestions but they're just suggestions of course, it's your site not mine. they're probably bad suggestions anyway :p
-add an international/random board or simply add flags/ids to random. this will help a lot to create a nice tight-knitted community of users who know one another, just like old /bant/. if you would rather your site focus on anonymity, you don't have to do this, but i think it's something that's lacking in most imageboards.
-ban porn dump from random
-don't add porn boards if you choose to ban porn dumps from random. there's no need.
-don't start with too many boards, i would only start with the random + meta (question & answer?) boards t.b.h
-over time add some more boards but not too many. i suggest adding comfy hobby boards, which could make your site stand out a bit. stuff like cooking, oekaki, nature, fashion. however this comes with the con of less traffic to these boards because they're more niche hobbies.
-promote OC as much as possible. boards like oekaki can help with this. maybe even make a board dedicated to OC where users can post whatever they've created. try to recreate that early internet feel.
-listen to the suggestions of your imageboard's users. your site is initially going to get a small amount of posters who try it out, and if you're lucky(tm) you'll get a niche group of active posters. these posters might lean toward talking about certain topics, and if they do, you might want to make boards dedicated to those topics. i think creating a small, dedicated site like this is better than trying to draw people in with boards. listen to what your users suggest on your /qa/ meta board too. it's important to get new users to join your site, but it's also important to keep active users posting so it doesn't get ded.
good luck, OP!