I'm bad at starting new topics as well, as writing in English. So, please, be prepared for enormous language violation and horrific meaningless expressions, that I've certainly done in these few lines and pray you to excuse me for. While being stuck somewhere for a little while — in a huge boring public queue, or a bus, or a train, or even in an airship with that horribly annoying kid, who is always somewhere around and proves himself very enthusiastic about torturing your ears for the entire flight and so on — I'm very likely to check my notifications from different resources just as many people do. And when it comes to such resources as Everypony, I wouldn't like people around me to give some curious glances at my screen. It is quiet disturbing, even if it does not occur very often. Don't get me wrong: I really appreciate current logo and all of four themes. But I would like to have something less conspicuous in order to avoid undesirable attention. That is to say a very minimalistic theme with a primitive colour scheme, no logo at all, and no site's name, and maybe a possibility to hide avatars/pictures. I'm certainly going too far with this suggestion, which is, I think, a bit outlandish to you and does not even deserve your attention. However, if one day you really have no clue, what to do, you may at least think of it.
I would as well~ I don't mind if people glance at my screen, but it's insanely awkward when they start asking me, "Oh, is that a forum? A pony site-isn't that for little girls? What's this? Why are there ponies? Lol, a pony site: what are you doing on there?"
So, it would have the default Xenforo Theme but with a logo that says 'PERFECTLY NORMAL WEBSITE.COM'. Gotcha! In seriousness, not a bad idea.
You could always have the header say "EP Forums" or something like that. And every once in awhile, an animated Pinkie Pie pops up and yells "HEY! THIS GUY IS ON A MY LITTLE PONY SITE!"
What does the default Xenforo theme look like? Some kind of this feature actually existed in the forum I've come from. Sometimes it may be quite creepy.
Now I'm developing themes for the site I can make a theme specifically for phones so that it looks better on phones and in your case less fancy pony imagery to keep it simple. I will add this to the Thread Development thread.