How to structure image directories for SEO?

We are currently reorganizing some files on our site, and I am trying to figure out the best way to organize files to be SEO friendly.

Here is the wrong way to do it:

yamaha-bikes\yamaha-bikes.php

The right way:

bikes\yamaha-bikes.php

My question is how do I go about organizing images for those products? Obviously if I throw a million bike images in my folder, it will be very disorganized, but would it be SEO fr开发者_如何学Goiendly?

In other words, should I do:

images\yamaha-bikes\yamaha-bike.jpg
images\yamaha-bikes\yamaha-bike2.jpg

or

bikes\yamaha-bike2.jpg

Obviously the first option is easier to organize, but is it as SEO friendly?

I would consider having more descriptive names, for example: images/yamaha/yamaha-gladiator-bike.jpg images/yamaha/yamaha-YZF-R15-bike.jpg

Remember that "-" are usually treated as spaces so you have the best description that would probably match what a user would search.

Also consider also importantly to use good ALT tags in the IMG that you use to link them to reinforce the name.