… title says all
I too had the daunting task of finding fiverr peeps to do banners/landers way back (before I got into media buys and was doing SEO and selling banner spots on the sites)
The biggest problem for banners gigs were their ridiculous turnaround time, if you want it in 24 hours you must take an extra gig usually.
So, when I got into media buying in last august, I started with a F/T designer because f*** waiting so long. The design team has ballooned into 3 people, and they also do design orders that come in for banners&landers.
I have always had better luck on Odesk than fiverr for this type of stuff. The price is not much more either.