Creating User-Hacks ... help needed

I'm thinking of creating several hacks for vB but i could need some general info, maybe anyone could give me a hint:

For example:

I'd like to display an indiviual image for every registered user - and the user should be able to change this via profile ...

So i added a field called "userimage" into the end of the table user (type varchar(100)). My thought was to create a variable called $userimage and to display these in the profile and threads ...

Now i'm seeking the part where the data of an user is read for display in vB - could anyone help?