This will convert all the ico files in the folder to gif. It uses the final frame of the ico file to create the gif.

for i in *.ico; do convert `mogrify -identify $i|awk '{print $1}'|tail -n1` $i.gif;  done

I had a collection of ico files with the ext gif - these are the commands I used to fix the situation…

rename .gif .ico *.gif
find . -name '*.ico' -exec convert "{}" "{}.gif" \;
OR
mogrify -format gif *.ico
rm -f *.ico