i would like to make a simple avatar system for my users. 

Usage is simple, every uploaded avatar image is named by user, for example: 

`<a>...$username.'.jpg';..</a>`

so there is really no need for database. 
When user is logged in, I just append the filetype to the already (from database) required username.

What concerns me here is the default image, which is used before user sets his own image. What is the best way to handle this? Is there a possiblity to create / copy default image to users avatar folder when user account is created?

I know that I can achieve this using database (default value) or checking if user image is set etc. but i want to keep it as simple as possible.

Thanks in advance :)