We used a comfortable office chair that we already had... I just took the right arm off of it. Height adjustable, rolls easy, swivels - it has worked out perfect as a "guitar chair." My wife bought a comfortable leather chair, so she and he cat could enjoy the "concert seating." A bookcase gives me a place to keep "stuff" right beside my chair. Since the room is small, I added a double amp stand to get the amps off the floor (stacked). Off The Wall guitar hangers keep my guitars within easy reach. Living in a tropical climate, our whole house has tile floors - we bought an area rug for the guitar room to soften the sound a bit.
We're a long ways away from the house currently, so I can't post photos. Sit in the room, decide what will fit best where... try that as a temporary situation, then start making holes and buying furniture! I don't have a "man cave," but I am delighted with my guitar room.
Best wishes,
Jim