Add ability to set default box front image to use for thumbnails if no image is defined

[Former user]

Please give users the option to replace the default thumbnail (box art, that is) that's shown when no front cover for a game is available. Ideally by allowing users to set an image file globally or per platform to stand in for the default "empty" thumbnail, rather than mass-adding a cover image to manually-selected games.

[MrArcade]

I second this... A default thumbnail if no metadata exists for that game within a platform is something that I would appreciate

[daniel emes]

i third this...