These icons are 25x25; the files that are appended _small are 16x16

To use the regular 25x25 icons in Classic Shell Explorer, use these settings
on the "Toolbar Settings" tab:

Big Buttons: Checked
Small icon size: 16
Large icon size: 25
Menu icon size: 16
Text is on the side: Unchecked
Same size buttons: Checked
Resizeable toolbar: Checked

Individually specify the regular 25x25 icon files for each toolbar button.

If you want to use the _small icons, then UNCHECK the "Big buttons" check box,
and individually specify the icons files appended with _small.

(If you use 25x25 and uncheck "Big buttons," or use 16x16 and check "Big
buttons," then the icons will be scaled, reducing image quality.)

I recommend the following sites for .ico conversion from png with
transparencies:
http://image.online-convert.com/convert-to-ico

You can use the following site to batch convert 25x25 icons to 16x16 with good
quality:
http://convertico.com/
