Media websites can get very creative in their approach to packages, especially as a founder you will know the effective ways you can craft messages to your audience that are honest, direct, yet unintrusive at the same time.
On the other end of the table, sponsors have standards which they use to measure vales of what's worth paying money for in a package. Direct to customer email blast, front page video ad, homepage take over, site wide ad banner campaigns, to name a few.
Often media companies present a three tier package offering with different price points and levels of presence. Depending on the brand who is the sponsor, the higher level doesn't just mean "take over of all real estate in our website" but can be something more interactive such as a charity auction event or interview with a celebrity that you have connection to. Be aggressive on your pricing even on the low end and it will help determine the appetite of the sponsor.
Of course, all packages are designed knowing what messages or products the sponsor is trying to get across, so let them educate you about them before putting anything together. If they hold big promises, don't be afraid to fly out and meet them in person. When starting out, the cost for travel is the cost to learn about the business.
Lastly, metrics is everything that makes or breaks the deal. Your unique monthly visitors, unique monthly registered users and a US/international break down is already enough to tell 80% of the story to your sponsor. If your unique is not spectacular as you're only starting out, focus on your growth rate and engagement rate. Having a story to tell on how much longer your users engage in your site, or how much clicks/posts/likes they make mighty shine a different light if your uniques are not up there yet.
Do note that most sponsorships are A LOT of work and is almost guaranteed to deter you from the vision of your business. I'm sure you don't wake up every morning and think "where is a good place for a skyscraper ad". :) Maybe the time for sponsors is not now but later, when your stats can command 5x or 10x the money for the same amount of work. That can only be determined by you. Good luck!