You need a callback function that is called each time a new image is entered in the fileselect. This function will then send an update message to the image control. I have no idea how to do this with InstallOptions. But I do know that nsDialogs has built-in callback functions that you can use for just this purpose:
http://nsis.sourceforge.net/Docs/nsD...l#ref-onchange
And in any case, nsDialogs has superceded InstallOptions a long time ago. I recommend you look at the tutorial in the nsDialogs readme:
http://nsis.sourceforge.net/Docs/nsD...adme.html#step