In impress, you have toolbar buttons to easily add a shadow and crop an image. It is not possible to add these buttons into a toolbar in writer by customizing a toolbar.
that's true, you can't have those functions in Writer toolbar.
the crop image button is only available in Impress (and Draw) but not supported in Writer. see: Bug 34555 - Make cropping handles for images (as in Draw/Impress) available for all LibreOffice applications(In reply to Jay Philips from comment #0)
anyway there's a nice extension called CropOOo (compatible with LibO too) that resolves this problem until a specific Writer crop button will be implemented.
download and install it from: http://aoo-extensions.sourceforge.net/en/project/cropooo
regarding the image shadow I don't know if there's any extension to workaround this.
As crop is tackled in the other bug report, then lets limit this one to just the shadow button (.uno:FillShadow) which works on shapes but doesnt work on frame-type objects like images in writer.
Migrating Whiteboard tags to Keywords: (needsDevEval, topicUI)
As images in writer are treated as frames and not like shapes as in draw, the uno command should work on shapes in writer.