why do icons only show up on my computer ??

[ChrisW67]

Is that true in general for QT, or only for the (absolute ref'ed .dll) calls from qcore4.dll?

Other parts of Qt, for instance SQL support, load plugins on demand and check all the relevant plugins to see which, if any, supports the demand. Plugins provide a mechanism to extend the library without the library having to know about every possibility ahead of time. All the library knows ahead of time is the defined interfaces that a plugin must implement. It is a common idiom for extension.