Twitter has been reaching out to ad agencies in recent weeks with an interesting brief: It's looking for ideas on creative ways to market the service and build the Twitter brand.

It wouldn't be surprising for Twitter to seek agency help. Facebook made its famous (or infamous) "Chair" video spot two years ago and just recently released three new video ads created by Wieden + Kennedy.

Now Twitter has been inviting agencies to pitch concepts. It's not clear whether the work will include TV, but it is understood that the media spend will be low. No surprise there: As the Oscars Twitterpalooza showed once again, Twitter gets plenty of free exposure on TV, but it could distribute video across its own considerable network, not to mention Vine.

Twitter is thought to be looking for something less than an agency-of-record relationship but more than project work. Executives familiar with the matter believe the company would like an agency it can turn to on a project basis.

Unlike Facebook, Twitter does not have a CMO, though it does have a small consumer marketing team. With all the free mentions on TV -- prime-time and in the news -- one could argue it hasn't needed it. But now Twitter's growth is slowing down. The fourth quarter of 2013 was Twitter's slowest quarter of growth yet.

Twitter said it averaged 241 million monthly active users in the fourth quarter, only 9 million more than in the third quarter and an increase of less than 4%, the lowest quarter-to-quarter growth rate since Twitter began disclosing those numbers.

Twitter's challenge is to get non-users to join and dormant users to see its value, so it would make sense that they'd want to start telling their own story in a more accessible way.

Twitter has dabbled with agency relationships before. The company in 2011 enlisted Edelman for PR duties to educate consumers on the virtues of Twitter, though that relationship eventually fizzled. In 2012, agency West created a TV ad for Twitter for a Nascar partnership. Twitter also worked with Interpublic's Huge on a project basis.

Contributing: Cotton Delo