How to create ico file with more than one image
Newer versions have an easier command:
convert -background transparent image.png -define icon:auto-resize=16,32,48,64,256 favicon.ico
-background transparent
is of course optional.
Found it on imagemagick.org site:
convert image.png -bordercolor white -border 0 \
\( -clone 0 -resize 16x16 \) \
\( -clone 0 -resize 32x32 \) \
\( -clone 0 -resize 48x48 \) \
\( -clone 0 -resize 64x64 \) \
-delete 0 -alpha off -colors 256 favicon.ico