Add a option to adjust the background

[0Elverum]

When I set up a background it ever adjust to the left... You need to edit the image before to apply a aspect ratio that fit with your screen. A option like "adjust to the left/center/right", or maybe a interface to adjust it will be ok

[hiSandog]

A small set of predictable fit modes—cover, contain, stretch, and original size—plus horizontal/vertical alignment would handle most screens without requiring an editor. The settings view should preview the actual launcher viewport and persist crop position independently of the image file. Tests with portrait, landscape, and ultrawide images can verify resizing does not reset alignment or distort aspect ratio unexpectedly.