Modern Teenage Man Cave Interior Design

Spencer's Man Cave

Masculine

Morning light

The old, nasty carpet; it is going to be replaced, so need suggestions. The carpet will be the same throughout our upstairs, so it needs to also be suitable for the other rooms upstairs: Spencer's bedroom (black and grey there too), a guest room (light grey walls, more feminine decor, periwinkle blue/white color scheme) and an exercise room (Sherwin Willaims/Repose Grey walls and exercise equipment, so black and grey tones).

Though newly painted, the wall color doesn't seem right. It is Sherwin Williams/Repose Grey, which I chose for being grey with beige undertones... sort of like the sectional, which is medium-ish grey. It is comfortable & inexpensive, so I won't care when my teen & his friends cause spills and stains. But back to the paint... what ended up on the walls was not mixed properly, because it is fairly different that the sample quart we tested. In addition to having too much of a "blue-ish tint", it seems too light for a teen "Man Cave"

Need to keep the sectional, the TV & console, pub table & chairs. My son also wants to hang the "Full Send" flag on the wall (sorry!), over the love seat portion of the sectional. Oh, and the "bean bag chairs" (which are really foam stuffed, and fun and comfortable). The teen boys love them, BUT I'm willing to get different colors if that helps - they were cheap!
Need a ceiling fan (we live in Texas and even with A/C, the warmer air funnels upstairs, so fan really helps), but willing to get different color/style.
Willing to remove the shutters... though they help insulate from the Texas heat.

Yes

Paint

Yes, Carpet

Here's the Deal: Spencer is my only child, and a really, really good kid, so I want his last years at home to be fun and memorable. That said, he has picked some...uhmmmm "quirky" things for what he is calling his "Man Cave". I have 4 years before he is off to college, and I want to make this a space that he feels is "his" and that he is happy/excited/proud to invite his friend over to enjoy. In another 4 years, I can re-decorate again. In the mean time, I want something that incorporates his previous "design selections" (sorry!!), but helps pull the space together in way way that keeps me from cringing too much. So at a minimum, we need new carpet, new paint color (I think???), possible built-ins for fridge and snack storage (need help with that: Should we add them? Color? Include upper cabinets? Or possibly just open shelving?), and LOTS of ideas for wall "art" and decor accessories.

I don't need this to be "timeless", I just need a 15 year old to say "Thanks Mom, this looks REALLY Cool" (which is probably a much taller order than "timeless"!) On the other hand, I don't want to spend a lot on the decor items... we'll probably be changing it in 4 years... other than the mini-fridge thing, as my husband will probably replace the sodas with beer and have sports-watch get together's up there once my son is off the college.

Hope that helps, looking forward to working with you!!