How about a flag that gets set whenever a player goes on a wall, like that of a chest, eg:
##ow#level32.graal#32#32
Only if the player actively moved onto the wall, not teleported.
Also, a screenshot could be saved locally with a new command, such as:
NPC Code:
if(onwall(playerx,playery)) {
setstring server.onawall,#a;
snapshot playerx,playery;
}
The first command being another way(excluding server-source editing) to tell some server-side npc to jail a player, and the second's command parameters being the focus of the screen on the level.