Background pattern purple #1998
 Colorful  CC 0

Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i

Source Firkin

 More Textures
Prismatic Groovy Concentric Background 3 No Black #459
 Noise  CC 0

Prismatic Groovy Concentric Background 3 No Black

Source GDJ

Psychedelic Geometric Background No Black #382
 Noise  CC 0

Psychedelic Geometric Background No Black

Source GDJ

Prismatic Abstract Geometric Background 4 No Black@2X #443
 Dark  CC 0

Prismatic Abstract Geometric Background 4

Source GDJ

Colorful Paw Prints Pattern Background #260
 Noise  CC 0

pixabay.

Source GDJ

Grilled Noise #581
 Fabric  CC BY-SA 3.0

You could get a bit dizzy from this one, but it might come in handy.

Source Dertig Media

Dark Circles #306
 Dark  CC BY-SA 3.0

People seem to enjoy dark patterns, so here is one with some circles.

Source Atle Mo

Wood@2X #50
 Wood  CC BY-SA 3.0

Dark wooden pattern, given the subtle treatment. based on texture from Cloaks. https://cloaks.deviantart.com

Source Atle Mo

Green Dust & Scratches #107
 Wall  CC BY-SA 3.0

Snap! It’s a pattern, and it’s not grayscale! Of course you can always change the color in Photoshop.

Source Atle Mo

Background pattern 214 (colour 4) #2373
 Yellow  CC 0

A seamless chequerboard pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i. Alternative colour scheme.

Source Firkin