set i to 1
set pathName to "PATH TO PARENT FOLDER"
set childfolder to "city/"
set frames to 99
repeat
    do shell script ("cp " & pathName & childfolder & i & ".gif " & pathName & "/city.png")
    set i to (i + 1)
    tell application "GeekTool Helper"
        refresh geeklet "city"
    end tell
    if i is equal to frames then
        do shell script ("cp " & pathName & childfolder & 1 & ".gif " & pathName & "/city.png")
        set i to 1
    end if
    delay 1.0E-3
end repeat