Image lists are Windows system objects for holding an ordered list of icons, and they are represented by handles in Windows. OpenDCL encodes image list handles as entity names when returning them to AutoLISP. These values are not really entity names, but they can be passed to OpenDCL functions that expect an image list, and OpenDCL will interpret them correctly as image list handles. Use the Image List methods to manage image lists.
All images in an image list share one width and height, in pixels. That size is set when the first image is added to an empty list. In Studio, the first picture you import determines the size, and the width and height fields then become read-only. In AutoLISP, you may pass optional Width and Height to dcl-ImageList-SetAt when adding the first image; otherwise the first image's native size is used. Later images are scaled to that size. The size cannot be changed afterward. To use a different size, delete every image from the list and add them again, starting with an image of the desired size.