Google maps instead of grdimage

For example I have google type of map
nakarte.me
How can I include it in the script , if I already have there different other things
I need this in one format or coordinates

I think the only way you could use that in a GMT script would be to save it as an image (e.g, PNG) or a geotiff if that is an option, then plot it with GMT and add stuff on top.