One of the greatest accomplishments any marketing leader can have is the development of their staff. This goes beyond the individual development plans and goals you have for team members and includes the cohesive development of a group of professionals who support each other, leverage each other's strengths and abilities and strive to each more together. I've been privileged in my career to lead teams that I've inherited as well as built teams up from the ground floor. Both have their good points and their challenges, but the goal to both is clear - create a team that support the mission of the organization and effectively implements marketing strategies and tactics.
If you're set with what marketing needs to do for the company, it's then about setting the vision and attributes that you want in your team, lining up the structure required to met those goals and see how current team members fit or start recruiting for those skills that you need. It's like trying to change tires on a car that's moving down the highway, but eventually pieces will fall into place.
The vision you want for the team must include the standards and expectation you want in team members and the group as a whole. This will define the culture the group has over time that in the best of circumstances the group will reinforce and strengthen over time. If your team has a strong set of expectations they all buy into they will defend the culture and nuture it well beyond what you can do from your office.
Structure is important in the sense that you should know where pieces should fit in the puzzle but don't sacrifice talent and effectiveness for structure's sake. A good team should put talented individuals in positions to contribute, even if it doesn't fit neatly in an org chart. You need a starting point, but don't be afraid to improvise if it helps the team perform.
The most important item is to always remember that your team is never built - it's always in a stage of being built. A regular evolution of where team members are in their particular career path balanced against the needs of the team and the organization is critical to insuring that your department is in step with company needs and vision. The worst position you can be in as a marketing leader to have a team that doesn't match the rate and speed of what is needed by the enterprise, so it's important to take stock of the players and the team at regular intervals to make sure you are on track.
If you can make this happen, you will be rewarded by looking back on the people you've helped and influenced over time and see how they've succeeded either within your organization or beyond it. A great marketing leader's overarching mission should be to create the next generation of marketing leaders. If you can do that you'll be remembered well beyond your tenure.