Custom Folder / Finder problem

Hey,
ive recently switched over to mac, (after using them at college for a year) and these forums have been a savior to me for a few things so far!

I did a quick search and couldn't find anything so im sorry if this has been answered 100 times.

anyway, im having a small problem customizing my folders, basically i have a picture as a background and want to have the folder open in finder at a fixed height and width so that it doesnt have this white border round the area the picture doesnt cover, heres some pictures of what i mean.

what folder actually opens as:


what i want it to open as:


If anyones really interested, its for my university interview when im showing work and looking through folders. (im a graphic design student) So it really needs to look good aha! ;D

Try dragging the folder onto the desktop, open it from the desktop, resize it and then close it. It should remember the size the next time you open it.

that works when im opening from the desktop, but when i drag it back to the folder i want to keep it in the size changes again back to the same as the root folder.