The broadcaster has approached several agencies regarding the pitch, which is expected to take place later this month. The brief is likely to include both online and offline communications.
Picnic was unveiled by Sky last year, but Ofcom has yet to authorise BSkyB to extend its paid-for TV model to digital terrestrial television. The service is now expected to launch next year.
Customers will be able to choose any combination of the three services under the Picnic banner; Sky will also sell its broadband service as a standalone option.
To access the service, customers will need to use a new generation of DTT box, which will not be subsidised by the broadcaster. Box manufacturers will be free to set their own specifications, such as an additional PVR, and retailers will set prices.
The first manufacturer to offer a Picnic-compatible box will be Sagem. Other manufacturers are set to follow suit.
Customers can register their interest in the service on a microsite, picnicnews.com. Sky will release further details of the Picnic package nearer the launch, but the broadcaster has confirmed that it will be offering its most popular channels, including Sky Sports 1, Sky Movies and Sky One, as well as a children's and a factual channel.
At launch, the Picnic service will be available to nearly three-quarters of all UK households.