How can i add a field to upload account picture in salesforce

This requirement seems like Display Picture in Contact

In this post a complete solution is provided to add picture on any object detail page.

You only need to change logic in DisplayImagesController class and its page as you are fetching details from social site. Some integration need to be done.

If you face some problem you can post/comment your problem here.

There are two free AppExchange packages that will do this well:

• Salesforce Labs' Picture Uploader
• MK Partners' Photo Uploader

The other, even simpler alternative is to add a Rich-Text custom field to the object in question. I don't think you can restrict it to only photos, though, so the user-training hurdle might be a bit higher.