All designs / Backgrounds / Patterns and textures
Olive wood grain close-up
Patterns and textures The photo fills the whole card. Your callsign and contact details go on a light or dark panel over it, and you can choose which at the design step.

A sample station on the light panel, with the photo lightened 20 percent so the writing stays clear. The design step lets you choose the other panel or change the dimming. The bare photo is below.

Photo: "Olive-wood-364426" by Stefan Schweihofer (stux), CC0 1.0, via Wikimedia (https://commons.wikimedia.org/wiki/File:Olive-wood-364426.jpg). Free to use on your cards.