Am worried about background image

hello,

i want to create a background for my website ( not yet started ) and i was going to use an image to make it look better but then i thought about screen resolutions and i was wondering what size i could do it without the quality of the picture being lost

thank you.

I've used an image with the width 1350 px. That should fill the whole width of the page on most resolutions.

If your background is a "repetitive design" instead of one large image,
you could tile that smaller image across and down your screen, so it
wouldn't matter what size it was.

Also by tiling the image, as mlseim said, it will cut down on image load time.