Honestly, based on your current site and what it is that you do I'd go look into an Open Source CMS, find a theme you like and go from there. There's Joomla but I find it to be a bit "heavy, cumbersome" in areas. Or just get WordPress and install a gallery module.
Both are Open Source, free. Admin is all web based so your operating system is not an issue and there are huge support communities for both.
Joomla!
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