Hi Pilippe,
I don't think Dataform is meant to replace the Database activity. Instead it can do everything Database can plus a whole lot more because of the extra field types included in it. When you install Dataform, it is totally separate from the DB activity.
As for already made CSS or js templates, I don't know if there are any available and I personaly have not tried any in the DB activity yet. I just don't have that many database activities in use and I just never seem to find the time to experiment with it. I would suggest making a simple DB activity, and then try playing around with the CSS template and see what you can come up with.
The documentation for Moodle 2.4 for the CSS template doesn't have any examples but the Javascript template does. Check it here.
AL