I think I am going to start replacing my roommates ugly decor in a slow manner.
Would it be possible to compromise with your roommates instead?
No. One of them works in a fucked up company, so he has no control over his own life
You may not like your roommates' decor choices, but this is their home as well, so you should let them do as they please with their own spaces. It's rude to touch their things without asking, and you shouldn't be disposing of things that belong to them.
I am not concerned. Either way, in the end I really just want it to be my way.
You should really talk with your roommate before starting to replace what is not yours. This is going to become a huge issue and may result in you having a pretty big fight with your roomate.