100%, absolutely go ahead!
On the subject of giving Asterion a hat, the main thing holding us back from doing so is the way his horns are layered, really, since the layering usually goes
>fur color layer
>body layer
>a LOT of clothing layers
>emote layer
>nose ring layer
>headwear layer (stuff like glasses, etc)
>horns layer
>horn accessory layer
Asterion's horn shape will be customizable in the future (though there are already sprites for this) so it's a layer on its own.
Adding headwear like hats or crowns becomes an issue because for most of his sprites, it would have to rest between the horns, so we'd have to split the horn and horn accessory layers into two, so
>fur color layer
>body layer
>a LOT of clothing layers
>emote layer
>nose ring layer
>back horn layer
>back horn accessory layer
>headwear (glasses, etc. but could also allow hats, crowns, etc)
>front horn layer
>front horn accessory layer
It's... kind of a lot. And there's an additional complication: remember when I said "most of his sprites"? The layer order for the front facing sprites would have to be the same as the original, or else the hat would clip between horns. An alternative would be to have all the front facing horn sprites on the back horn layer and not render the front horn/accessory layers if asterion is front facing, I suppose.
And that's not getting into the trouble of shaping the hat to acommodate all these horn shapes. So, it's doable, but very complicated. You have our blessing to try, though.
There may be some spoilers if you code dive so do it at your own discretion and try not to spoil other people though.