Wall filter breaks when rows and cols aren't aspect ratio compliant
try something like :
vlc --vout-filter wall --wall-rows 3 --wall-cols 1 --wall-element-aspect "4:3" video.mpg
(where video.mpg is a normal size video)
The vouts don't work well since the filter is trying to fit a 4:3 video on 3 4:3 vouts ... (which isn't possible unless at least one of these 3 vouts is empty ... simple math)
if you change --wall-element-aspect to "10:3" ... it'll work well.