Yes, you may be able to stack a number of texture packs. You can activate them at the same time however, other texture packs might not load when they are positioned lower. Except if the previous texture pack on the list does not have that texture pack modification or alteration. The texture pack which is positioned higher on your list would have load priorities.
When a texture pack is being loaded, it is added to the list of active packs on the right side of your resource packs menu screen. Minecraft's load order is chronological. This means that it will look for assets on the upper part of your activated textures packs list.