[Maristany]

In the code you provided it says background instead of background-image, but it seems you're using the right code. The thing is, that first continue shopping button is around 350 lines inside your custom theme and is an image of the Beige Theme, maybe you activated it and you're adding your customizations there? If that's the case it'll work if you don't add many modifications, but can become very messy if you do.

Just a thought, hope this helps.