For the gif
Go to
And then choose "upload" Your preferred/Prepared
Gif image.
You can make your own animated pictures "Gifs" from any kind of video cip.
Or you can make pictures animate.
(Which is a little time consuming to learn/do )
...................
For the free ones/Made one.
Just Google yourpicturename.gif
"That is moving picture/animated ".
But for the copyright issues, if they /might happen
Use Google advanced search
And look for only free to use images.