Maybe something like this, using all Gimp tools.
There is a texture filter that goes way back into the dark ages of Gimp. Filters -> Artistic -> GIMPressionist and one of the textures is canvas. A quick overview.
(1) The most important layer. Selected / Copied / Pasted in place. Then the GIMPpressionist texture applied. That does not look too good, all horizontal and vertical lines, so half of it deformed to the tent 'slope' using the Handle Transform tool. That bit duplicated, then Flipped, then positioned with the Move tool.
(2) Once-upon-a-time everyone made their own drop shadows. New layer under, the tent shape in black and Gaussian blurred. Moved into place according to (perceived) light source.
(3) The direction of the shadow determines any shading on the pitch of the tent top. Make a selection, fill with black, adjust the layer opacity.
There is a texture filter that goes way back into the dark ages of Gimp. Filters -> Artistic -> GIMPressionist and one of the textures is canvas. A quick overview.
(1) The most important layer. Selected / Copied / Pasted in place. Then the GIMPpressionist texture applied. That does not look too good, all horizontal and vertical lines, so half of it deformed to the tent 'slope' using the Handle Transform tool. That bit duplicated, then Flipped, then positioned with the Move tool.
(2) Once-upon-a-time everyone made their own drop shadows. New layer under, the tent shape in black and Gaussian blurred. Moved into place according to (perceived) light source.
(3) The direction of the shadow determines any shading on the pitch of the tent top. Make a selection, fill with black, adjust the layer opacity.