Hi - I would use the replace or reskin tool for this.
You can both just try generic prompts like
“beautiful backsplash that matches the kitchen” to let the AI choose or something more specific like “add a white tile backsplash”
You can also use a style image if you have an image of a backsplash you’d like to apply (you’ll need a decent style image that shows the backsplash installed close but not too close so the AI knows the scale)