You should really be consistent in all forms of media to have a solid, recognizable voice. Any visual representation of your company should in some way convey the branding of your company. Not to say everything should be a carbon copy of the other elements. A photograph should be able to convey an image in the same “voice” as an art element.
For example, a Target commercial presents itself in such a way that you can tell it’s a Target commercial before you even see the logo. The choice of music, the style of the footage shot, the cadence of the editing…something just “feels” like Target even before you know it is.
This goes much further than a trademark or a logo. It is a continuous message, image or feeling that carries through everything that comes from your company.
To build a brand you must determine what you’re trying to convey and to whom it is intended. It may be a lifestyle, emotion or status. The key is to check everything against the message of the brand. This allows a lot of freedom in design styles as long as it supports the message of the brand.
The goal is to differentiate and to create a unique brand. The challenge is to hold that together in a unifying voice.