Hexagonal pattern #2379
 Dark  CC 0

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

Source Firkin

 More Textures
Batthern #324
 Grid  CC BY-SA 3.0

Sometimes simple really is what you need, and this could fit you well.

Source Factorio.us Collective

Background pattern 1 #220
 Noise  CC 0

A pattern derived from repeating unit cells each derived from part of a fractal rendering in paint.net.

Source Firkin

Paper texture filter #149
 Paper  CC 0

Filter simulating the texture of heavy paper.

Source Kelan

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

Prismatic Groovy Concentric Background 3 No Black

Source GDJ

Prismatic Basic Pattern 2 No Background@2X #448
 Noise  CC 0

Prismatic Basic Pattern 2 No Background

Source GDJ

Snowflake remix #155
 Dark  CC 0

A bit simplified version. Although it could be edited out to be simpler. Anyway, this time the tiling is converted to a pattern fill -which is using clipping for the tile's edges.

Source Lazur URH