Screenshot on Unity Play cut off

Hi there, I'm just working my way through tutorials and publish the little excercise projects. I can add a screenshot, but most of it will always be cut off. Looking at other peoples projects it seems to be a me-problem, but what could I possibly do wrong?

Example: https://play.unity.com/mg/other/webgl-builds-126618 Or: https://play.unity.com/mg/other/webgl-builds-126307

Edit: It really just seems to be a scaling issue when the used image is relatively small. Using a large (~full hd) image works fine.