You have two background options: twelve preset gradients, or an image you upload. You can also flip text color between light and dark depending on what looks better on your chosen background.
Step 1
On the Trainer Card Maker sidebar, find the Background section at the top.
Step 2
Click Gradient to pick from twelve color presets: Crimson, Ocean, Champion, Forest, Sunset, Ice, Void, Berry, Steel, Lava, Mint, Lilac. Click a swatch to apply it.
Step 3
Or click Image and upload your own background. Any image works. It crops to fill the card.
Step 4
Use Text color (Light or Dark) at the bottom of the Background section if the card text is hard to read against your background.