The EVE Online dev blog title was too good to pass up and features information about how exactly in-game sales of vanity items will work. CCP Zulu also indicates that the team is going to be watching PLEX prices very closely to maintain the economic balance.

My PLEX prices!

If you're concerned at this point that this will in some way impact PLEX prices then we're ahead of you there. We'll be monitoring the PLEX market extremely closely and making sure certain equilibrium is maintained in pricing. We have various tools to ensure that, but the most important one is keeping Aurum as a separate currency with set conversion from PLEX.

So this thing is vanity items only?

Yes. We will start out with a rather limited number of items initially, carefully measuring the demand and how it impacts the economy. As time progresses, we'll gradually introduce new items and revise our strategy. We've also discussed this issue in depth with the Council of Stellar Management and will both consult with them and keep them up to date every step of the way.

Read more on the EVE Online blog.