How to randomly choose one image from a pair

If this template helps then use it. If not then just delete and start from scratch.

OS (e.g. Win10): Win10
PsychoPy version (e.g. 1.84.x): 3.0
Standard Standalone? (y/n) If not then what?: y
What are you trying to achieve?: My stimli are 30 paired images. I want to randomly choose one from a pair to present. So each participant will be presented with 30 images and the 30 images will be different across participants. Can someone help me with this? Many thanks!