Sources of Textures

Plain colour texture files can consist of say 64 x 64 bit images created in your favourite image editor. Easy to do, but a bit bland. You can add noise to your image at pinetools.

WebsiteReview
3djungle.netThere are 5,599 seamless textures to choose from at the last count. Subscriptions: 4 plans, starting at $5 for 30 days.
polyhaven.comGood quality seamless textures. Free, though subscriptions welcome.
3dtextures.meFree.
sketchuptextureclub.comLow and medium res textures are available using the free account. These are appropriate for Studio models. High res and further textures are available with their premium service.
cloud.blender.org/p/texturesA library of more complex texture files. This is a premium service costing €9.90/month at the time of writing.
poliigon.comSome great textures. Some textures are free but the full service is chargeable, starting at $12/month for 4 assets.
freepbr.comOver 500 free PBR textures or download all of them for $16.00.

Sizes permitted by the Studio must be in powers of 2, such as 64px, 128px, 256px, 512px and 1024px square. Large sized textures should be reduced in size to say 256px to reduce the graphics processing load in the Studio.

Texture files should be .png or .jpg file format.


Example texture image of engineering brickwork