[Typo3] TypoScript: does filename have to be a constant

[Matt Valenti]

When specifying a file for an image object - does it have to be constant?  I 
can find no examples where the filename is generated using TypoScript or 
PHP.  For example, I'd like to use a file based on the page_id (it could be 
image1, image2 , image3 etc.).

    10 = IMAGE
    10.file = fileadmin/images/image1.jpg

The only way I can think of is creating a huge condition statement.  I was 
hoping there was a better way!  Thanks!