well i was about to post a link to some freeware wallpaper changers that can change wallpaper at specific intervals, until i realized this is not sufficient. you really need to be able to tell it to change to a specific image at a specific time, regardless of when started etc.
i think this is worth coding.. im not sure ill get to it this weekend, but i'll comit to doing this, at least in some form.
i was thinking to have it parse a file that could specify what images to show and when. for example:
// First the settings (position can be: center, tile, stretch, max)
position=center
// Then the files (file= DATEMASK|TIMEASK|FILENAME, where:
// DATEMASK is of the form DD/MM/YY-DD/MM/YY
// TIMEASK is of the form HH
// and * is allowed
// and FILENAME is relative path
// if multiple times match due to wildcards, the earliest match will be used.
// if multiple files are specified separated by ; then one will be chosen randomly
// For example
// */*/2005 - */*/2006 | *-* (the entire year of 2005)
// */*/* - */*/* | 01-02 (1am to 2 am every day)
//
*/*/* - */*/* | 01-04 | image1.jpg
*/*/* - */*/* | 04-08 | image2.jpg
*/*/* - */*/* | 08-12 | image3.jpg
*/*/* - */*/* | 12-16 | image4.jpg
*/*/* - */*/* | 16-20 | image5.jpg
*/*/* - */*/* | 20-24 | image6.jpg
or
12/25/* - 12/26/* | 01-24 | christmas.jpg
*/01/* - */10/* | 01-04 | image1.jpg
*/10/* - */20/* | 04-08 | image2.jpg
*/20/* - */32/* | 08-12 | image3.jpg
as for dragging wallpaper position and size.. i'll leave that for another more visual wallpaper tool.