question about the I-129F form?

Question

in the instructions it indicates that the passport sized pictures have to have a white background, is that true or does it really matter

Answer 1

If the pictures don't have a white background you are likely to have the whole package sent back to you with insructions to complete it again.
Every last detail must be correct. On a good day a worker may overlook some small detail but you can't rely on this. Every small mistake slows the processing of your application as you will be asked to resend anything that is incorrect.
My i-129(f) was sent back as we signed it all in black ink and the idiot who opened the package decided the signatures were photocopied and sent it back to be signed again.

Answer 2

Yes, that is true:

"Give USCIS a passport-style color photograph of yourself and a passport-style color photograph of your fiancé(e), with both photos taken within 30 days of the date of filing this petition. The photos must have a white background, be glossy, un-retouched and not mounted. The dimension of the full frontal facial image of you and your fiancé(e) in separate photos should be about one inch from your chin to the top of your hair. Using a pencil or felt pen, lightly print the name (and Alien Registration Number, if known) on the back of each photograph."

You can send something else and then they will just send it back.