OpenStego v0.5.0 has been released today, and it adds support to process multiple cover files in one go.
The "Cover File" box in the GUI now allows selection of multiple files. It also supports wildcard characters - '*' matches any number of characters and '?' matches exactly one character.
For example, if you want to embed a given message in all PNG files in "C:\test" folder for which the name starts with "image", then you can give Cover File value as:
This feature would be particularly useful when you are using OpenStego as watermarking solution. You can select all you images and embed your signature / copyright message in bulk.