There's actually quite a few different ways to make this happen. I'll briefluy descript 2. One method, a filtered portal, requires FileMaker 11.
With a filtered portal, you can add a field to your layout for selecting the specific clip with a script trigger on this field to run a script that refreshes the window to force the portal to update. A fliter expression compares the ID number of the image record you selected in this field to the ID number of the related image records to control which image is visible.
By creating a relationship that includes both the vidoclip record's serial number and this same type of added "filter field" you can just add the image container field from the related table and selecting/entering an image ID number brings up the selected image.