Dimmed lighting (like shut off the lights in the middle and leave the ones
at the sides if you can)
A velvet rope (like at the movies) (crepe paper would work, too, I guess)
Hushed talking (good luck!)
label the artwork in really tiny type on transparent labels in a pale color
of ink, like tan....and then mount the labels exactly in the shadow cast by
the artwork...and really low....so they are virtually impossible to read,
even if you can find them.
A sticker to put on their lapels when they come in.
A big clear box for "voluntary" entry fees, but block the door with it so
they have to suck in air to get around it, then glare at the people who
don't put in anything. (sound familiar?)
A "gallery guide" to pass out with artists statements.
A gift shop with smaller versions of some of the artwork (that could be
really funny if you could do it far enough in advance - have kids reproduce
their own or each other's work on "merchandise" "inspired by..")
A gang of girl scouts sitting on the floor in front of the very piece you
came to the big city to see....(just kidding)
If you covered the hanging space with dark paper, you could paint elaborate
"gold" frames on it in tempera & mount the work inside the rectangle. (I saw
a gallery show like that once, of silly watercolors. The artist had painted
trompe L'oeil frames on the wall around each piece work).