Make a multi-resolution favicon.ico from a source image, using ImageMagick
Keep it Short and Simple
convert image.png -background white \ \( -clone 0 -resize 16x16 -extent 16x16 \) \ \( -clone 0 -resize 32x32 -extent 32x32 \) \ \( -clone 0 -resize 48x48 -extent 48x48 \) \ \( -clone 0 -resize 64x64 -extent 64x64 \) \ -delete 0 -alpha off -colors 256 favicon.ico