Team banners want symmetry and a colour you can shout. Swap the base dye and the same three layers turn a blue pennant into a red one, which is how a minigame arena gets eight teams out of one design.
Blue Pennant
Blue base · 3 layers · Stripe Top / Stripe Bottom / Rhombus
White bands top and bottom frame a red diamond. Change the base to any of the sixteen dyes and you have a team kit in one click.
/give @s blue_banner[banner_patterns=[{pattern:stripe_top,color:white},{pattern:stripe_bottom,color:white},{pattern:rhombus,color:red}]]
Forge
Black base · 2 layers · Gradient Up / Bricks
A red glow fading up out of black, with brick courses on top. The closest you get to a lit furnace wall without a texture pack.
/give @s black_banner[banner_patterns=[{pattern:gradient_up,color:red},{pattern:bricks,color:brown}]]
Stadium Banner
Lime base · 2 layers · Straight Cross / Stripe Top
A white cross on lime, capped with a green roof stripe. Reads like a pitch from above, which is exactly what you want above a minigame arena.
/give @s lime_banner[banner_patterns=[{pattern:straight_cross,color:white},{pattern:stripe_top,color:green}]]
Four Quarters
White base · 4 layers · Square Top Left / Square Top Right / Square Bottom Left / Square Bottom Right
Four corner squares and you have a racing flag. It is the only design here that uses all four corner patterns, so it doubles as a test of your loom stock — and a good base for a team crest.
/give @s white_banner[banner_patterns=[{pattern:square_top_left,color:black},{pattern:square_top_right,color:black},{pattern:square_bottom_left,color:black},{pattern:square_bottom_right,color:black}]]