Geograph - photograph every grid square

If your friend asks you to and for some reason cannot create their own account then that's fine provided they understand the Creative Commons licence. You should credit them as the photographer when submitting.
See related article: Photos not taken by submitter

You can, as long as you now hold the copyright in the image, which will be the case if you've inherited them. During submission, you will be asked in step 4 to confirm the Creative Commons licence. You should untick 'I am the photographer' and enter the name of your deceased relative there. The picture will then show on your profile but will be credited to your relative. Alternative, you can change the credit after submission by clicking 'change image details' under the photo and then 'change credit' after your name.

If you are sure that you hold the copyright but there are several possible deceased relatives which could have taken the picture, you can submit them under a name such as 'Smith family archive'.

If you have taken the picture yourself, or you have inherited it from a deceased relative and are certain of the copyright history, the age of the photograph is of no consequence.

With regard to old postcards or photographs without provenance, although the photo may well be out of copyright it is incompatible with the Creative Commons share alike licence and cannot be accepted on Geograph.

If you have taken a current view of the same place and would like to link it to the old photograph you can submit the recent shot here and upload the old photo to the media repository http://media.geograph.org.uk or a photo-sharing site like Flickr and link to it there in your description.