You can bring any images into Spine. If you don't use the script for Photoshop (or Gimp, Inkspace, Affinity, etc) then you'll have to position the images in Spine yourself. That just takes a few minutes, unless you have a huge number of images. The alternate is to write an export script for Sketchbook Pro, though I'm not familiar with it so I can't say how hard that would be (but likely harder than positioning the images).