At the current time the only way one can search the Gallery is through the captions - i.e. the title that the poster chooses to give to the piece they display. The description one adds to the picture is not included in the search.
I wonder if it is possible to add another field or set of fields when one posts an art work or reference picture indicating keywords under which the item may be searched. This would be in addition to the caption and description.
For instance: let's take this picture I uploaded recently. I titled the photo Sunrise over calm waters. If I could insert keywords I might have chosen something like: Landscape; sea; clouds etc. This might be useful for anyone searching for references, perhaps even more than the caption itself which sometimes is not very helpful.