[TYPO3] Image Processing - which user - and where?

[Patrick Schlaepfer]

We moved our server to a managed server. So no root privileges left.
The image processing part of typo3 now creates the images
under user "X" but only with rw right for user "X". - Assuming
it's the webserver user.
The ohter user "Y" now can't delete (clean typo3temp) the
files, nor read.
Where can I change the behavior of the image creation
process in typo3. I'm using GM.

Old server typo3temp (apache runs under httpd)
-rw-r--r--   1 httpd   1364 2007-05-05 15:26 tmb_f325461241.jpg

New server
-rw-------   1 admin   1364 2007-05-05 15:26 tmb_f325461241.jpg