Decals aren't a big deal anyway, it's just if you want to see all level numbers from jump maps back. But there are several kinds of decals with different names. I'll have to dig into my own config to get you the right commands, if you're interested.
EDIT: okay, I think I got it.
The kind of decals you found is actually the temporary decals (bullet holes in walls, explosions marks etc. Basically things that disapear after a while, in that case, you can only have 9 displayed at once. Which is okay but feel free to change that value. Don't touch the rest, imo.) and the kind of "decals" that I was talking about, previously, are actually named "overlays".
And the command to turn them ON/OFF is the following (I personnally put it in my autoexec file so I can remove it easily, same goes for any command that differs from the main config, I put everything in the autoexec AFTER the config execs)
r_renderoverlayfragment 0/1
I hope it helped. But just as r_3dsky 0/1, it's a matter of visual preference. I used to jump on 4starters with a glitchy sky because I was too lazy to fix it and because it only is actually annoying for 2 jumps in particular (the skip jump in E course and a telesync in D course iirc).