Learning Toolbox automatically creates optimised and resized images to reduce the use of Internet bandwidth without losing image quality.
For tile background images you want to make sure that your cropped image – the square or oblong cut-out that you create using the LTB imagepicker – has at least 400 pixels.
For your mini-Poster image you need to make sure that the cut-out has at least a 1000 pixel width left, especially when you aim to have it printed.
Don’t worry about measuring this exactly, you can just try what it looks like using the LTB app or the stack preview.
Related help pages
- How do I add a background image to a tile?
- How do I adjust and crop an image?