The ideal sizes for the drag and drop backgrounds are:
- width 900 px (if it’s larger, the scroll will be added, if it’s smaller, it‘ll be left-aligned)
- height 758 px (this is the max height, but it can be smaller)
The same sizes will work for the hotspot question.
The single choice image question: the placeholder size is 250x200 px. If you want to add a larger image (so that it's possible to zoom it in), the size would be 600x480 px.
Section icon: 290x170 px.
Course logo: 200x50 px (it will be auto scaled if you use other sizes).
The main background image: the size of your screen. If you want it to appear full-screen, just disable the secondary background.
The secondary background is displayed in the repeat mode, so using a solid color or a pattern if preferable.