Help with psychomotor task

[Christian Potter]

I am creating a psychomotor task with 7 blocks, using the ImageDisplay to show a slide with four squares. The ImageDisplay objects alternate between all the squares being blank (with a random duration time) and one of the squares being filled in (fixed duration). 

Since there are going to be 240 slides in each block (1680 total) I am looking for a way to make them more efficiently than Copy + Pasting each of the 5 different images (in an already determined random order) in the BlockProc window. Ive looked online and the closest I've come to finding anything are tutorials for making nested lists with words, but I haven't found that useful since I have to follow the determined order that they're in and I can't do something like cycle them. 

If anyone knows how to do this better using the BlocList or something else I would appreciate it. If not I would also appreciate any link to a resource where I can learn about it. 

Thanks.