This is by far the most common shelving question. The answer depend on how heavy or strong the shelf wall is. Shelf weight is not downward weight. Weight on the front of the shelf has a much larger effect that weight to the back of the shelf. Its best to first develop some rough drawing showing the items you will want on the shelves, and then to add the weights of these items. With this info we can understand both weight and weight position and engineer your booth to exceed the stability needed for the shelving and product you want to display.
As a general rule 10 pounds per shelf is no problem and very common. 30 pounds per shelf is significant and will require changes to the shelf and wall to meet this load bearing requirement.
Yes, this is very common. We use quarter inch thick glass with polished edges. We often make shelves that are longer or not as deep. In some situations, such as in a tower structure, we are able to provide larger shelves.
Each circumstance is different and we may have suggestions to help you better, safer accomplish your glass shelf goals.