Agreed, GOOD pics make a huge diff!
And the better the description of the part and it's condition is, the better chance you have of selling it.
Over the past few years I've only had a few purchases go south on me. I completly got screwed out of my money auction. Another was an item that was supposedly shipped but I never received it, and then was replaced with a damaged item. The most recent (about 2 years ago) was an item stated as "rust-free" and in "useable" condition - it was neither. The seller did end up refunding all of my money, but I had to resort to leaving him bad feedback and filing a complaint.
I chock up not having any problems/issues as a seller to providing plenty of info, part numbers if available and their application(s), being prompt in answering questions before/during/after an auction, and of course shipping quickly.
I've never charged a handling fee, so that may factor into it as well.
Within a 2 & 1/2 week period I watched 3 diff KZ650 seats in fairly equal condition sell for vastly diff prices. The first sold for about $22, the second sold 4 days later for almost $150, and the third one that ended a week later brought $43.
Seasonal does play into it, but I think it's a gamble anytime you list anything - sometimes you cash in BIG time, and other times you barely break even.
About 4 years ago I bought a '77 KZ650 basket case from a guy locally. I kept the wheels, brakes, oil cooler, frame (gave that to Mark Wing), and the cases.
The rest I listed on ebay, and ended up pocketing almost $700!
Did the same with the '82 GPz750 I drove over 500 miles round-trip to get for about $119.
Made enough on eBay that I not only recouped what I paid for the bike, but also enough that it paid for the trip itself and I still made about $200 on top of that!
Sometimes it's a buyers market, sometimes it's a sellers. AFAIC it's just like gambling, you just never know when you're gonna hit it big.