I just tried this in Construct 3 but nothing happens. I tried a single file and choose for random image:
-> TiledBackground: Load image from choose(?"bgCastle.png"?,?"bgDesert.png"?,?"bgForest.png"?,?"bgTrees.png"?) (cross-origin none)
I try again in C2, maybe its a C3 problem. Thanks!
/edit: works fine in C2. Seems to be a problem in C3. I created a bug report for C3.