Sorry, but the PS3 is not visible from a PC as if it were another PC.
The best way is to use a USB drive to copy all the photos you need to the PS3.
Note: It may happend that once you plug the drive to the PS3 and try to access it from the photos section, it will say like there are no files. Use triangle -> "Display All" over the drive icon to explore it.
I'm using SimpleCenter for such a thing. Search it. If you have a wireless router and are broadcasting your Internet you can do it.
Once you are running SimpleCenter you add your media to it. Videos, Music, Photos and such. Then on your PS3 you should see the SimpleCenter icon under Photo, Music and Video. If not you click Search for Media Servers. You can then copy anything you added to the SimpleCenter library to your PS3 harddrive. It's pretty easy.
Then again why waste the space on your PS3 when you can just streaming all those to your PS3 :) Well maybe not HD videos. They don't do so well if you have a mediocre Internet connection. Music is great!