mIRC doesn't allow you to move a control once created in a dialog, but a dll like dcx.dll can. You could script it with /did -g and a timer if you could extract all frames from the gif.
You could write a dll (though I suppose you are not familiar with language which can create dll like C/C++ delphi..) but you would still need to know about gif structure etc. It would be easier to find a piece of code made by someone and to try making a dll from it but again if you have no idea about dll creation, it's not going to be easy.
I think it would be a nice addition for mIRC to have support for gif built-in.
