The easiest way to do this is define a custom fill pattern (8x8), then would not have to use an image.
https://sdk.play.date/1.9.1/Inside%20Playdate.html#f-graphics.setPattern
You'd just to playdate.graphics.setPattern(pattern) and playdate.graphics.fillRect(0, 0, 400, 240)
Pattern maker web interface: https://devforum.play.date/t/gfxp-useful-lib-tool-for-working-with-patterns/906
Another way is to create a screen size blank image at runtime, load your 10x10 image, and do tiling yourself by drawing the small image repeatedly into the blank image (once, at start up).