abstract
attention
backdrop
background
banner
barrier
black
blank
caution
construction
danger
design
diagonal
dirty
equipment
grunge
hazard
industrial
industry
line
metal
old
outdoors
pattern
risk
road
rough
safety
scene
shape
sign
site
space
stop
street
striped
stripes
surface
symbol
texture
textured
traffic
transportation
urban
wall
wallpaper
warning
yellow