Thanks for your reply

As for your database (singular) The structure of a database works as follows:

Database->Table->Record->Field

You only need 1 database which you will have 1 table for users and 1 table for your images.

To give you an example of how this is like Pascal...

Think of a Table as a Record and each variable within the record with it's own type. (INT, VARCHAR, DATETIME, FLOAT, etc...) A database is really just a series of tables that you can access to retrive the records you want with a query string. (in the form of a SQL command)

Here is the mysql page in the PHP manual: http://ca3.php.net/mysql

You are looking to go through this process:

1) Connect to your DB server (know your server address, username and password)
2) Select your DB
3) Run your query string! (some knowledge of SQL helps; http://dev.mysql.com/doc/refman/5.0/en/sql-syntax.html)
4) Fetch the next record from your results into a record object. ()
5) Access the fields using the returned associated array. (Not the only way, but this is a heck of a lot easier!)
6) Repeat 3 if you need more data...
7) Close DB Connection!
Actually I allready knew that (I've taken a database course at uni). I just wasn't focused on the database aspect and failed to use right terminology. My bad ops:
I wouldn't recommend Java as it requires the installation of an extra runtime, which for some is not convenient and some just don't like it. You can just as easily get the same quick loading effect using the AJAX technology and a little know how.
I don't think it would actually be a problem if the users had to use a runtime enviroment like Java. Actually I believe that most user for this app would allready have it installed.

Do a quick google for the 'XMLHttpRequest' object. There are some really good tutorials on it's usage and functionality, I think you'll find it completely changes the way a webpage becomes dynamic!
This seems interesting and I'll look deeper into it. If I can avoid using Java and still get a result that I'm satisfied with using AJAX technology I'll go that way.