Currently, there are two types of sales landers at Undeveloped (that I am aware of).
The first is where you just change your nameservers to Undeveloped (like @cabotower mentioned) and don't do anything else. An example of this type of lander can be viewed at Flipticle.org.
For the second, you still change the nameservers but you can add a .png logo and corresponding social media links (what they refer to as a "brand package"). You can also customize the lander with one of 3 color schemes. An example of this type of lander can be viewed at Fliptical.com.
You'll notice that each type looks different. Also, both types give you the option to add a description that will show up under "Seller's notes about this domain."
There is no additional cost associated with using the "brand package" lander, to the best of my knowledge. @Bob Hawkes is right--if you pay to have a logo made by someone else, then yeah.