I hope I didn't miss an existing thread about this, but I couldn't find one.
I remember that I noticed this bug before some time ago and wanted to report it, but forgot about it again. I don't really know anymore when that was exactly, so I'm not sure since when it is happening, it probably didn't start recently though. But since I racechanged one of my chars who's got an indrik mount from dark elf to khajiit, I've been noticing it more frequently.
As long as she's mounted and not moving, her eyes are crossed. They appear looking forward normally, when the mount is moving, but as soon as it stops, the eyes are crossed again. It's only happening when she is on the mount, not when she's standing/walking/running on her own.
Crossed eyes on an indrik:
Eyes while moving & standing:
I tried the other indriks too (but not the dawnwood one since I don't have it) and it's happening with all of them. Then I tried other mounts I and she's looking forward normally on horses, bears, camels, guars, wolfs or senche mounts, not on the Eldersblood Peak Ram though. She has her eyes crossed in the preview for the Yorgrim River Ram and the Ram of Dark Delights too, so I think it might be happening with all cervines. Since I only have the one ram and the indriks and there aren't any other cervines in the crown store to preview at the moment, I'm not able to check that though.
Eldersblood Peak Ram:
Horse & Senche mount:
It doesn't matter if the char is using an outfit or a costume, wether there are body or face markings, personalities or skins. It's always there. My other khajiits have the same bug too, so probably the gender (2 female, 1 male char), class (1 necromancer, 1 nightblade, 1 dragonknight) and alliance (2 AD chars, 1 EP char) do not have an influence on it either.
Male DK on ram, indrik & horse:
I tried both the ram and the indriks on my other chars to see if it is happening there too and I didn't find anything wrong on my dark & high elves, bretons nor my orc (I don't have any imperials, wood elfs or redguards). But on my two argonian chars (1 male, 1 female) it seems to be happening too, even though it is much less noticable and irritating because of how their eyes are formed/placed.
I'm not completely sure on my nord. Her eyes seem to be slightly crossed, but I forgot to look at another mount to compare her eyes, so maybe she's always looking like that.