Could always make your own ?
I'd suggest trying to make your own too. I couldn't find any good blanks on a short google and deviantart search. :/ Sorry.
Please read my FEAR/Portal/HalfLife Fan Fiction!
Repurposed
Should be relatively easy to do.
Start with a blank 'wall', either white or light neutral color.
Create a series of horizontal parallel lines.. these will be your 'foot' lines (4', 5', 6'). Bump the line weight up just a tad.
Duplicate the set, and offset the whole set down by 1/3 the distance between the lines. Duplicate and offset again. Unweight these lines back to default.
You should end up with a horizontal 'grid'... thick, two thin, then thick, two thin, thick..
Then put numbers to the right and left sides of the thick lines, or slightly above them... descending from the top. Put an apostrophe after each number ( 6' ).
Finally... find a wall 'texture' (cinderblock or brick) to watermark the image... and import it into your scene as a lineup wall! Scale appropriately, add harsh white lighting from the front... "Turn to the right!!!"
"City of Heroes. April 27, 2004 - August 31, 2012. Obliterated not with a weapon of mass destruction, not by an all-powerful supervillain... but by a cold-hearted and cowardly corporate suck-up."
I've looked and I'm tired of looking.
Does anyone know where I could find a blank Police line up backgound.
Here's an example
I'm no photoshop expert so I won't even attempt to try to cut the villains out of that pic. At this point any blank police line up will do, but I had my heart set on the background from the pic in the link.