This tiger camouflage would make sense if this plane was flying over the desert.
It could have been painted that way simply for safety purposes or for special events.
In the case of this particular version of the MiG being used as a trainer the bright and contrasting color scheme would make it visually stand out better if it ever crashed anywhere on the Polish landscape.
NATO countries hold "Tiger Meets," multinational exercises and professional exchanges where participating aircraft, including those from Poland, are painted with tiger patterns.
Some Polish air squadrons traditionally used "flying tigers" as emblematic mascots since their first founding. I couldn't find any explicit explanation for this choice of mascot but it might be related to the historical use of animal furs by Polish hussars, who wore fur over their armor. While leopards are commonly cited, there are also historical depictions of tigers being used.