Man cave wall decor is chosen by subject, not by style. Almost nobody picks a palette for this room. They pick a thing they care about, aircraft, a flag, a car, a course they have played, and the room is built outward from it.
That makes it one of the easier walls to get right, and it changes the order of the decisions. Subject first, then scale, then how dark the room already is.

Four subjects carry this room
Flags are the largest group by a clear margin, usually weathered rather than crisp. Then transport: military jets, warbirds, classic cars, ships. Then service and military scenes. Then sport, with golf courses the most common because a course photographs as a landscape.
What those four share is that each one is a statement rather than a decoration. A flag on planks or a fighter in formation tells you something about the person whose room it is, which is the actual job here. Man Cave Wall Decor holds all four.

Dark rooms need light inside the frame
Most of these rooms are basements, garages or converted spare rooms, and most have one window or none. A dark artwork in a dark room with one lamp disappears, which is not the same as looking moody.
The fix is to choose images that carry their own light source. A jet with sun on the canopy, a lit skyline, a course at low sun, a flag against bright sky. All of them hold on a dark wall in a way a black and gray composition does not. The navy wall art guide covers the same problem for a dark palette.

Scale is where this room usually goes wrong
The common mistake is buying too small, because the room is often narrow and the instinct is to match the wall rather than the furniture. A 24 x 16 canvas over a full size sofa or a pool table reads as an afterthought.
Use the same rule as anywhere: about two thirds the width of the furniture beneath, so roughly 48 inches above a 72 inch sofa, with the center 57 to 60 inches from the floor. Above a bar or a pool table there is usually more clear wall than in a living room, so this is one of the few rooms where the top of the size range genuinely fits. Horizontal work runs 1 Piece, 3 Horizontal, 4 Pop, 5 Star and 5 Pop from 24 x 16 up to 82 x 42 inches. The sofa sizing guide has the measuring method.
One statement piece beats four medium ones
A wall of several mid sized pieces on unrelated subjects is the default outcome here and it rarely works, because each one argues with the others and none of them wins.
The stronger pattern is one large anchor on the main wall and everything else smaller and clearly secondary, or grouped on a different wall entirely. If there are genuinely several subjects worth showing, give them a shared thread, all aviation, or all the same era, or all in the same palette, so the group reads as a collection rather than a pile. The gallery wall layout guide covers the grouping case.

Vehicles photograph better than logos
A large part of what people want in this room is a team, a badge or a specific athlete, and almost none of that can be printed by anyone without a licence. It is the reason the category looks thin at first glance.
What is freely available is the machinery and the place: aircraft, ships, cars, stadium architecture, a course at dawn. Those carry the same enthusiasm without the licensing problem, and they age better than a roster that changes every season. Aviation Wall Art, Car Wall Art and Golf Wall Art are the three biggest lanes.

Flags are the most requested and the most specific
A flag is the strongest statement available and the least flexible. It is the same design every time, so what varies is condition and context: crisp and saturated reads as formal, faded and frayed reads as history, painted onto planks reads as rural.
The caution is that a flag is a statement before it is a picture, so it should be chosen deliberately rather than because the color suited the room. The American flag guide covers condition and the carved wood alternative, and Patriotic Wall Art is the wider range.
Quick answers
Common Questions
What kind of wall art suits a man cave?
Subject led rather than style led. Four groups dominate: flags, transport such as jets, warbirds, classic cars and ships, military and service scenes, and sport with golf courses the most common. Each one says something about the person whose room it is, which is the job that wall is doing.
What size wall art works in a man cave?
Bigger than instinct suggests. Use two thirds the width of the furniture below, so about 48 inches above a 72 inch sofa, centered 57 to 60 inches from the floor. These rooms usually have more clear wall than a living room, so the top of the range, up to 82 x 42 inches, genuinely fits.
How do I stop artwork disappearing in a dark basement room?
Choose images with a light source inside the frame: sun on a canopy, a lit skyline, a course at low sun, a flag against bright sky. A dark composition in a dark room with one lamp vanishes rather than reading as moody. Hanging it where a lamp reaches also helps.
Can I get team logos or athlete photos on canvas?
Not from most print sellers, because logos, badges and athlete imagery are licensed and cannot be printed without permission. The unlicensed alternatives carry the same enthusiasm: aircraft, cars, ships, stadium and course photography. They also age better than a roster that changes each season.
Is one large piece better than several smaller ones?
Usually yes. Several mid sized pieces on unrelated subjects argue with each other and none wins. Use one large anchor on the main wall, with anything else clearly secondary or grouped elsewhere. If several subjects matter, give them a shared thread such as one era or one palette.