Hi,
To be honest, I would not recommend using Linux/Mono for any important production site running mojoPortal, it is hit or miss with each release of Mono and it has been that way for as long as I have been involved with Mono. If you have no choice but to run Linux I would say your mileage may vary as to how well it works and how reliable it is. You may be able to get satisfactory results but I can't promise it.
In the newer versions of mojoPortal we have bulk upload for images in the image gallery.
Images are stored on disk not in the db.
Hope it helps,
Joe