All of our servers have ImageMagick installed, as well as the GD image library for PHP. However if you set
$wgUseImageMagick = true;
on our servers, MediaWiki will try to adjust the server settings before it uses ImageMagick and then image operations, such as thumbnail creation, will fail, because our servers do not allow that (for good reasons).
Thus we recommend you leave that set to false and then MediaWiki will use the GD library which will be as effective as ImageMagick in almost all situations.