Sounds like these are good questions for the wordpress.org forum.
I doubt there’s a plugin for the istock download to your site. (I couldn’t imagine istock creating an API allowing people to pay for and dl images… but stranger things have happened) Is it too difficult to download to your computer them upload?
I have no idea what you mean by "WP blogid and access point"
WordpressExport is a plugin written for Apple’s iPhoto which automates the process of getting your photos onto your WordPress blog.
All you have to do is select your photos from within iPhoto and then fill in your blog login details on the WordPressExport panel. All your selected photos will then be uploaded and resized for you and a thumbnail gallery will be posted to your blog.
If you happen to have a newer iPhoto (and thus, according to a few sites I found on Google, unable to use WordPressExport for iPhoto), or if you want to save some upload/generation time (as this will be done on the server side :) ), then another option would be to utilize my ExternalFilePath-extension.
Once installed this will be your flow:
1. Select the photos you want to share in iPhoto and go File > Export > JPEG > Custom size (fill in whatever size you like, I’d say 640*480 or 800*600)
2. Upload the exported folder by FTP to yourwordpresssite.net/imgbrowz0r/images/MyIphotoAlbum ("MyIphotoAlbum" being the name of your album whatever).
3. Then login your WP-Admin, make a post/page with your template and add a custom-field of "galleryPath" with a value of "MyIphotoAlbum" (without quotionmarks). And you’re done !
If you don’t have an FTP client, here’s one for Mac or PC[/*:m]
The photo’s look even better (and saves the hassle of pressing the "Back"-button for your visitors), use a Lightbox !
([Check out Chris’ screencast to find out how to implement that into Imgbrowz0r) – Don’t forget to download my WordPress-version of ImgBrowz0r below though, instead of the one that Chris links to ![/*:m]
If you want to use this (and thus Page Templates in general) on Posts aswell, check out this plugin.[/*:m][/list:u]