For any multi-tile art, use: https://www.imgonline.com.ua/eng/cut-photo-into-pieces.php

Change to central snapping and square images.

Divide the original photo's resolution by 32. (i.e 128x128 would be 4)

Use that number twice. Use it for horizontal and vertical cutting amounts on the site, so you have 4 horizontal

You will get 32x32 split images.

To make the math easier, make sure the image is squared. You can add some "filler" to the image to make it a square, like this one's purple: https://cdn.discordapp.com/attachments/691954609056645140/692216003681320960/unknown.png

Once you've done that, resize your base image to reasonable dimensions. In the link image below when you remove the purple (it is 256x256), it will take up 48 out of 50 image slots ingame, so only use higher resolutions for pics that REALLY need high definition. 128x128 image pieces split up only take up 16 whole slots ingame, so strike your own balance, as long as the resolution is Square and divisible by 32.

Make sure the option is set to PNG-24 and make square parts is on before splitting the image on the site. Once that's done, it will now let you download a zip file of all the PNGs. You can now upload each of these PNGs individually to acpatterns.com and generate qr codes for each, and there you have a bunch of split patterns to line up on the ground ingame!