I use Irfanview to edit my pictures before uploading.
Free download for Irfanview
Also I try to keep my pics around 400 x 300
And it depends on the buyer and the auction if annoyance happens with too many pictures.
If your buyer is on dial-up and your auction is too graphic heavy with large size pics and too many..then they will back out of the page because it's taking too long to load in for them.
Also if I'm looking to buy oh...ok..here's an example. I just purchased a silicone cover for a Zune. I knew what I wanted, I knew what the product looked like, I didn't need lots of pics. Viewed the specs of the auction and hit buy it now.
When I purchased a car on eBay four years ago..I wanted a huge amount of pictures. I would also think if you were buying a collectible you'd want alot of pics.
On my ID that sells clothing...I try to have four pictures. Front, Back, and two close up for details. But if it's a nice vintage piece of clothing I'll use more.
That's one of the great things about Auctiva..you can use as many pics as you want and not be charged as eBay would charge you for additional pics.
Alot has to do on what you're selling and who your target viewing audience is.
Good Luck,
Donna