customize reports

Do you mean create a report layout in design view, only without any fields, then save it. Then copy it to a new name when you want to create a new report?

I have always used the wizard and then had to change everything. I did experiment with a design as you said. I was wondering about customizing my own theme. Is that possible?

You can define a single report as the Access default when you create a new report. This is not selectable at the time you want to create a new report however.
 
The only other way is to create a report and save it as a report and then copy and paste it into your project. It will immediately ask you to name it. This is how I do it anyway. I would be interested in finding a simpler way.