Perhaps replacing the images is not exactly the answer.
If it really is that your trying to show several pre-loaded images
in quick succession , then maybe putting each in a positioned
div , and fiddling with zindex,visibility,clipping values
or something of that ilk would work faster.
If it needs to be continuouse perhaps setInterval or setTimeout
could be used to pump the manipulation of the style attributes
so as to keep the browser responsive.
I think in an animation , actual image replacement is probably the
Anyway given the sketchy information I hope my response was
at least of some help