Two often underutilized ways to spruce up any exhibit area are to include items related to mathematics and optical illusions. Both subjects have demonstrated "holding times" for visitors and can often be developed inexpensively.
A recent article about an exhibition of mathematical art (including the example from Michael Field, above) highlighted both the beauty and science, visible in every selection. There must be a blank wall or other suitable space in your museum that could benefit from such an image.
Often times we think of math and illusion images as only 2D, but one of my favorite websites, suitably titled "Grand Illusions" shows how mathematics and optical illusions can become 3D interactive objects or toys. The Grand Illusions site also contains an online shop where you can purchase many of the items shown.
How have you used math or illusion inside your museum? Share your ideas in the Comments Section below!