ISIS, Middle Eastern jihadists and Muslim separatists in South East Asia are about as far apart as it's possible to be in geography and in their origins, but making a peculiar public spectacle of executing captives by beheading is something they've each done.
I suppose there may well be other reasons particular to their local cultures for the practice, but is there something in common Islamic tradition or history that gives the execution of a prisoner by beheading a particular meaning and cache for Islamic cultures?
There's a good amount of bias in this question if you think beheading is or has been received differently in non-Islamic society. The last person guillotined in France was in 1977. Beheading has been an extremely popular form of execution for most of European history. We just happen to live in a time where execution itself is viewed by most of Europe as being, itself, a cruelty.
That said, there are hadith that suggest that executions should be carried out with a sword. There are also, however, hadith that make it clear the point is not to exact suffering, that the execution should be as swift as possible. Without getting into 20 year details, that's clearly not what's going on here.
Nor is mass execution, execution of foreigners, etc. etc. a norm in Islamic history or culture.