I'm not at all sure that the 2xx7 devices have the capability to do that. Both my US 3597 and an AU 3597 i've accessed don't have either the Picture Viewer in Apps or the 'Pictures' folder with stock jpeg images like the 2012 2xx0/37x0 and 2013 2xx5/34x0/35x0 series. 2011 and earlier nuvis right back to 300 series have them in a folder named JPEG with the same capability to change the start screen. In those devices you can also add appropriately sized *.jpg files yourself and choose them as a start image. I have a 3790>3490 convert with a photo I took of the Brooklyn Bridge as a start image:

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@Colonel2701
If you don't have the Picture Viewer App in your 2597 then the only other way is to substitute the logo PNG pics in region 16 of the nuvi's non-volatile memory. This is done by modifying the extracted 16.bin file using GIR_Editor, creating an RGN file and then flashing it back either using updater.exe or flashing the 16.bin by the ldr.bin SD method. If that's what you want to do, there are existing threads with logo bins or you can extract your own. Search or ask for more assistance. If you want, you can post a request along with the picture you want and either Caty or I or Loly etc can make the SD pack for you: [Only registered and activated users can see links. ]. Or read this associated thread here too: [Only registered and activated users can see links. ] if you want to try it yourself. It's dealing with 37x0 but the principal is the same.