@Meemaw: Found "libmono0" in Synaptic. F-Spot now opens and runs. Unfortunately it's not my favourite programme but it's running. Is there a missing "lib" file or something that prevents Shotwell from opening? Shotwell is on my Graphics menu in Phoenix but has no icon and will not even try to open. Synaptic provides only the programme name and doesn't offer any other "lib" or similar to include with the download. This is what happened with F-Spot. It was a single file download appearing in the menu without an icon, until I added "libmono0".
Will download and try Mirage later today. Hopefully it is a complete download...
@joec: The GIMP has been with me since I first started using Linux in 2007 (with PCLOS) but I haven't really learned what it does and how I make it do what it can do. Thank you for the pointer to "meetthegimp.org" and suggestion to "look at Darktable". I'm curious as to what a "Darktable" is. I'll check it out later today or this evening.
"ristretto" (as well as "gthumb") gave me about 2.5 cm square (I'm Canadian, eh...) or one inch square spots on my computer screen. I no longer have either installed, hoping to work with Shotwell or, if necessary, F-Spot to download my photos in the "Photo" (a.k.a. "Pictures") folder.
Thank you for your suggestions.