When we had an Egypt themed VBS, we found another way to use our "chairs." We made "houses" out of them, and used these for our "Tribe Time" (which I believe was called "Family Group Time" that year).
I liked how a colored piece of cloth looked like a lintel over the doorway (pictured above). A tribe sign also decorated each house.
Inside we made less effort to cover up the chairs (ran out of sheets). We decorated with blankets and pillows for the kids to sit on, and various other knick knacks our tribe leaders brought. Each tribe got a camp-fire for their room...something left over from the previous Wilderness VBS.
While they didn't look perfectly like houses, the outside was still a lot nicer to look at than stacked chairs.
You can see two of our rooms in the corner of this picture...they looked nice with the marketplace tents. We had four in total, one in each corner. Having these rooms right in the marketplace made for less traveling (there was also two Sunday school rooms used, right outside our marketplace...but we didn't have to use rooms in our other building, which is a further walk).