+4  A: 

What about using imageList1.Images.Add()?

Jay Riggs
So crazy it just might work!
Chris Ballance
Hey, it can't kill you right?
Jay Riggs
+2  A: 

It sounds like you're trying to add several images included in a single image object. In this case you'd want to use

imageList1.Images.AddStrip(imageSeries)

From the msdn docs: "A strip is a single image that is treated as multiple images arranged side-by-side"

Daniel LeCheminant
You are absolutely right, sir. In my defense such a concept doesn't exist in the Visual Studio designer (whereas a competing product has supported it for 14 years)
Ian Boyd