For large numbers of photos, you can upload them to dropbox or google drive and add a link to the photo folder in your listing, which can make it convenient for potential buyers to see more photos in one place.
I've done this for items I've posted for sale here and on places like eBay and Facebook Marketplace that have limits to the number of photos you can add to a listing.
Willson 2900 TA-1 Euphonium - Denis Wick 4AM
Yamaha YSL-643 Trombone - Bob Reeves BrassArk 5G "Gladstone"
Yamaha YSL-8440 Trombone - Denis Wick 5BS
VMI 3301S BBb Tuba - Schilke Helleberg
Past:
York Preference 3067 Euphonium - Denis Wick 4AL
Benge 165F Trombone - Benge Marcellus
Wessex BR140 Baritone - Denis Wick 6BS
F.E. Olds Special Trombone (ca. 1941)