As we know, there is a limited number of custom field per object, even with Unlimited Edition as metioned here: https://help.salesforce.com/apex/HTViewHelpDoc?id=limits_general.htm&language=en_US
So, i would like to know if there is a way to have unlimited additional values per object? Could we consider to create a custom object that has something like a list of addtional attributes?
Any idea is highly appreciated.

As we know, there is a limited number of custom field per object, even with Unlimited Edition as metioned here: https://help.salesforce.com/apex/HTViewHelpDoc?id=limits_general.htm&language=en_US
So, i would like to know if there is a way to have unlimited additional values per object? Could we consider to create a custom object that has something like a list of addtional attributes?
Any idea is highly appreciated.

Please help me with this question and please correct me if I misunderstand anything.

I am developing a package, in this package, I created some custom objects. I also have my external Web Service and my external database. Please take a look at my picture for more details: 

As I imagined, when clients install my package from App Exchange, the custom objects will be added to clients side, so they have their own database. The content of custom objects in each clients will be different. Is it correct or not?

And another question: Do I have some kind of "global Salesforce database" (stored in custom objects) but all clients will see it?

Thank you very much for your time!
Phu Nguyen