Do you mean about centered design area?
http://screencast.com/t/dRdHoNC8
It’s possible.
Contact me on skype: magentosupportteam.com (Chung MST)

I understand, but i think background/overlay image need to same size. Becauuse all objects when add to design should below overlay image and above background image. So they need to same size to create design area visible for everyone can understand which parts will print in this design, which are not.

Hi
I found it in js/pdp/pdc/js/pdc1.js
The code:
/////////////Setting default info///////////////
PDC_setting = {
color_default: '#FF0000',
font_family_default: "Arial",
font_size_default: '20',
div_side_action : $('#pdc_sides'),
line_height_default: '1.3'
}
/////////////Setting default info///////////////

Red is #FF0000
You can change it to black.

Hope this help!

Hi Daniel
I think:
1. Started position in center. when add any item, i see them on center.
2. Change in js means: Change in general, it apples for all products.

Hope it help!

Hi
To change font size from start, you can open pdc1.js, the path is: /js/pdp/pdc/js/pdc1.js
Inline 29, you can change font_size_default to bigger number (default is 20)
http://screencast.com/t/x4xjHqkW1

I hope this help.