I am sure it is possible to sell on ebay and to add photos, using a mobile phone with camera. I buy all the time, but have not been brave enough to sell on that site yet.
I have, however, used Gumtree, which couldn't be simpler, using my laptop and digital camera images. If you know how to load your photos onto a computer you can't go wrong. When placing an ad you will be asked to browse to choose the picture and a window will show your files from which to choose.
I hope you will find someone to guide you through the first attempt.