Canvas extension resizing mode was the #1 request in the past year. Updated version of PhotoResize400.exe supports it. Rename it to PhotoResize1024x600x0.exe to optimize pictures for a typical photo frame.
The last number in the file name represent brightness of the canvas. Use 9 for white, 0 for black and 1..8 for grays. (Or choose a custom color via a command line parameter.
Another addition is the ability to specify a wildcard filter for processed files with a -z switch. Try -zaaa*.* to process files starting with aaa. Use -z????????.* to only resize files with 8 characters in file name.