Welcome to the forum Alessio. 
alessiograziani wrote:I try to pose the question in another way. Is there a way to use the model Page outside the WolfCMS container? I'd like to use it in a php page that is running outside WolfCMS container?
No. The Page model depends on the Record class which is available in Framework.php... In essence you'd be loading a big part of Wolf CMS anyway.
You might get it to work, but you'll get no support with regards to bugs, etc. in that configuration. For obvious reasons. (I hope they're obvious anyway) 
Anyway, in response to your original post...
Wolf CMS tries its best to let you do whatever you want in terms of design, html, css, etc... I've seen your site (very nice design
) and I believe its not very difficult to convert to Wolf CMS. As for your custom DB for your images... A model is very easily made in Wolf CMS and a plugin is also very easy (and low-effort) to make.
I'd probably write a simplistic plugin that provides a new model accessing the custom DB.
In any case, using Wolf CMS to host your site and include the custom DB is a lot less work than adapting or extracting parts of the functionality of Wolf CMS and insert them into an existing site. (which is what you're trying to do I believe?)
See the wiki and phpdocs for more details on Wolf's innards:
www.wolfcms.org/wiki/
www.wolfcms.org/phpdoc/