I want them to be stored in the ImageList with their original size.
This is not possible. Store the images as resources. [...]
Yes, it is possible
if all the images have the same dimensions. You just have to set the proper
Width and
Height in the TImageList; I just (re)tested with a set of 640x480 images and it works as it should. Of course, if the images are of different dimensions they will be cropped/scaled/whatever to the list dimensions, depending on how you add them and how several other properties of the list are set.
In fact, this is how you set-up a "normal" list for, say, 64x64 icons or whatever.
Only drawback is that if you load the images at design-time you may end up with a huge .lfm; in my test (just a form and an ImgeList with eight 640x480 images) it grew to a quite respectable 21,8 Mib