If you have pictures, you have the choice to either store them in an asset library or a picture library. What is the best practice here?

Asset library (a media library)
More info about the asset library: http://office.microsoft.com/en-us/sharepoint-server-help/set-up-a-library-to-store-image-audio-or-video-files-HA101828004.aspx

Pros:
- Has in-built support for the new digital asset content types: image, video, and audio files.
- Has a default thumbnail-centric view.
- Has an image preview.
- Supports automatic metadata extractions (and promotion) for the following image types: BMP, GIF, ICO, JPEG, PNG, and TIFF.
- Podcasting support thru RSS feature.
- Supports metadata navigation (see https://www.nothingbutsharepoint.com/sites/eusp/Pages/SharePoint-Asset-Library.aspx)
- Has a standard SharePoint 2010 menu (and therefore, has ribbon support).
-Centralized repository setup for digital assets (image, video, and audio files) for the organization.
- Allows Edit in Datasheet View, the Picture library does not. This makes bulk metadata management a lot easier.

Cons:
- Does not create a slide show of the pictures. This is an often used feature in Intranets. Example: A news article with a direct link to the slide show view of your company's last event or party.
- Although it is possible to email a link to the file (as is also the case in a Picture library), you can't easily embed them in an email or Word document. If you want to do this, you need to manually download the files you want to embed and add them manually to the email/document.

Picture library
More info about the picture library: http://agsci.psu.edu/it/how-to/use-picture-library-in-sharepoint-2007

Pros:
- Has a slideshow view of the pictures it contains.
- Can only contain pictures and is optimized for that.
- you can embed a picture directly into an email or Office document using the "Send To" action menu item.
- You can use the /_vti_bin/imaging.asmx web service to execute Upload/Download and other operations related to picture libraries: http://msdn.microsoft.com/en-us/library/imaging.imaging_members(v=office.12). Asset libraries don't have such a service.

With a Picture Library, users can easily send pictures (one or more) in an email (embedded in the body or as an attachment) or automatically add them to a Word document. With an Asset Library, users must download the files and manually create the email / document. Both have the option email a link to the file.

Cons:
- Does not have the larger thumbnail option of a picture when you hover over the item.
- The library menu is 2007 style, and thus looks different from other SharePoint 2010 libraries.
- Has a complicated way of uploading pictures using the "Picture Manager" application.
 

Conclusion
For pictures, the asset library represents the new choice towards the Digital Asset Management way of working SharePoint is striving towards. For pictures, it's the preferred choice, unless you really need a slideshow view. For other types of content, the asset library is the way to go.
 

Credits:
This Wiki page was inspired by the discussion at http://social.technet.microsoft.com/Forums/en-US/sharepoint2010general/thread/1272cf0c-095f-40d5-bde1-49f1fff70ba1

Please note: Also check out the SharePoint 2010 Best Practice Overview page at http://social.technet.microsoft.com/wiki/contents/articles/8666.sharepoint-2010-best-practices-en.aspx