Ah, I see what you mean now. Those people don't need to upload an image for it though. If they don't want to go through the effort of doing it, then they simply won't. But It's nice to have as an option for the players who are interested.
I do see why that could cause concerns. There are many condos with 100-200+ canvas' already and I have heard of people having FPS issues with certain places. Fortunately for me I don't really have issues with them, but my rig isn't cheap. With a 970 and it runs this game 90+ fps almost everywhere with everything on Turbo (highest settings), even with around a ton of items around me. Believe it or not, the worst lag I have experienced so far was some in some dudes home theatre. There were hundreds of spiders in it, covering the walls, ceiling, and most of the floor. As well as a shrine.
Just look at all the evil lagmonsters!
So my point there is anything we add will cause lag. Especially high-poly objects (Eg: Spider). It would be interesting to see a comparison of framerates between jetpack trails and some condo rooms. The trails would only activate when a jetpack is being used too, so the lag that is made from trails wouldn't be like the ones in GMT.
Perhaps this is another situation that could go with the options? For example, Canvas Options > Player Jetpack Trails - And you can toggle the canvas options on or off for specific media types. Like the Player Jetpack Trails, DVD/Game Cases, Body Pillows, Wall Canvas, etc: