To change the background colour select F4 to bring up the local menu. On this select COL and you get a colour side bar.
Select SPACE in the side bar and in the local menu scroll the colours by selecting the + or - in each of the 3 boxes to get the background you want. Scroll all 3 to 15 to get white. Some sytems have a local macro for this.
To improve the resolution you can edit the models graphical display by selecting (while in SPC mode)
GRAPHIC
MOD VISU
DISCRETN
a DISCRETIZATION box will come up change the sag to .01 and select the solid. It should sharpen your image.
As for tiff creation some systems have a seperate screen grab outside of catia but you would need to look around