And now, a suggestion that actually stands a chance of being implemented. Now that climbing is a thing, there should be a new class of wall-mounted traps designed specifically to combat climbers.
Weapon Trap--exactly the same as before, except they can only hold 1 weapon (which really should be true for the floor traps as well) and are, of course, mounted on a wall. They are designed in place by a Mechanic or Architect (on open ground, not an existing wall), and then built by a Mason.
Handhold Trap--Looks just like a perfectly good handhold/foothold, but breaks away once a load is placed on it, usually causing the climber to fall, and then it gets slowly pulled back into its original place by a hidden cord. Can be installed on natural or constructed walls.
Grease Trap--Pops out and sprays warm oil/grease over the tiles directly below, with some splatter to both sides. Affects both the climber that sprang the trap, and anyone who tries to climb those tiles for the next couple of days. Must be reloaded with oil/tallow after each use, as well as charcoal if it isn't already built in Warm stone.
Flip Trap--A spring-loaded block, slab, or other moving part of the wall that suddenly shoves outward, thrusting the climber into empty air. Same restrictions as a weapon trap.
Downward Spikes--not a trap, exactly. Just like Upright Spikes, except that they project downward at various angles, forming a strong deterrent to anyone wishing to climb up. Can be harnessed to a lever to make the spikes retract / extend. Can be built on natural or constructed walls.