My objective is to remaster a version of LXDE PCLOS for internal use. The background image needs to show a special logo.
I appreciate the developers looking into this background-crash-logout problem.
That will be easy to do.
Add the logo to an existing wallpaper:
Open the wallpaper with gimp. Drag the logo from the file manager over to the wallpaper and drop it. If you do not want it centered, click the Move icon (looks like an equal armed cross) in the toolbox (left side pane) and then lower down click the radial button for "Move the active layer." Now you can drag and drop the logo into the position you want. When you have it in position, click Image (on the toolbar) > Merge visible layers. In the message that opens, click "Disguard invisible layers." Click ok. Next click File > Save As. Give your new wallpaper a name and an extension. .png or .jpg will do. Do not save as an xdg.
If you want only the logo to show, open gimp > click File > New > give the resolution you want > in the newly opened graphic, click Layer > Transparency > Color to alpha. The default background color is white; the default color to alpha is white, so just click OK. This will give you a transparent background on which to drag, drop, position and merge your logo. This must be saved as a .png. jpg can not handle transparency.