Hi Dimitra,
Assuming you are willing to merge together the four blocks of experimental trials (otherwise the items sharing the same picture would never appear in a row to start with, since you seem to use each picture only once per block) you can make it work as in this project (I have updated some commands to match the modern PennController syntax — you also seemed to use the same code for all your trials, practice and experimental, so I use a single Template command)
Jeremy