Hi Richard - sorry, should have signed my message - it's Edith
With watermarking I normally do it via batch processing in Adobe before uploading, so not sure about script based solutions.
Interesting to hear your experiences, does validate my opinion that with Magento a good developer is vital, whereas with osCom/Zen you can much more "muddle" through. Not a reflection on your coding skills, just on the Magento structure. Just installing the dam thing on Xampp and upgrading the version turned into a lesson about command-line coding for me ... Still love it, but always recommend with a proviso.
All the best! Edith from TerraNetwork