Stims with different durations in a block

Hi, I am hoping to display 50 images randomly. However, I want 25 of those 50 images displayed at 1 second each, whereas the other 25 displayed at 2 seconds each. So the sequence would look like

Image 1 - (displayed 1s)
Image 2 - (displayed 2s)
Image 3 - (displayed 1s)
...

Is this achievable? Would appreciate any helps - thanks!