I had a quick question about armour in 5e. So I'm creating a fighter character who is wearing hide armour. However, I was wondering if I can make any look I want for my hide armour, or do I have to follow a specific look for the armour?
Up to you and your DM
The rules do not go into details about these sorts of things. The armor section gives a rough description, such as:
Hide. This crude armor consists of thick furs and pelts. It is commonly worn by barbarian tribes, evil humanoids, and other folk who lack access to the tools and materials needed to create better armor.
But this is more just so that there is a common understanding as to what hide armour is. If you want a set of hide armour that deviates from this generic description (but is mechanically no different), this is a detail to discuss with your DM, although generally, in my experience, most DMs will not have a problem with minor aesthetic changes, especially if it is unlikely to impact the mechanics in any way.
It is up to the DM, but do think of your other players, also. There are many who are turned off by things that don't fit into the general medieval D&D theme. So if the hide armor were to be made to look like Batman for instance, I can see that being a problem. Then again, unless you are going to have drawings and minis that look like Batman in your D&D session, maybe they would never have to know exactly what your PC looks like.