Yes, older photographs are welcome, as long as they were taken by the contributor, or a member of their close family (with credit to the photographer). Please crop any white border from a print, as well as any date stamp on the image, before submitting.
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
Very few images are rejected, but some of the main reasons for rejection include:
Digital Manipulation: Images that have been digitally manipulated in a way that significantly devalues the geographical information.
Subject Focus: "Family snap" type pictures where family or friends are the main subject. While people can be present in a photo, they should not be the primary focus.
Technical Quality: While we don't demand technically perfect pictures, images that are: Too small (fewer than 480 pixels along the longest side), Excessively blurred, So underexposed that details cannot be properly seen, or Pictures with distracting reflections (e.g., taken from inside a building or vehicle). Often, some judicious editing can improve these pictures for successful resubmission.
Date Stamps: Images with date stamps automatically added by the camera are strongly discouraged, even if not too obvious. If possible, please turn off this feature on your camera when taking pictures for Geograph (the date the image was taken is stored separately).
There are a few other reasons a picture may not be accepted, which are detailed in the main Geograph Guide, linked below
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'.
I am guessing this is a question as to the suitability of family snaps. The general rule is the people should be the secondary element of the photo rather than the main feature, and posed shots (it can be worked out in most cases) are more suitable to other photo sites as not related to the area they are in. Having said that a discussion thread has refined this recently, and the general conclusion was if there are local events or occupations which are taken spontaneously then a person featuring as the main subject can be included although without a reasonable amount of background would normally be added as a supplemental*. But for straightforward posed family snaps then the only circumstance they would be suitable is if they were a small part of the whole scene, and as with most the older the photo the more flexible the criteria.