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'.