I basically did the same with
Exciter.com when I was properly promoting it and it converted extremely well just based on text links alone. I later added one banner just to give it a more visual appeal and it enhanced sign-ups but only marginally - like less than 10%.
I subsequently left the biz and am selling the site but I have to say that if I was continuing with
Exciter.com and I had a grandfathered Overture account, I could probably convert good sign ups by firing $0.01 traffic at the site which is pretty decent considering todays TGP traffic. Having said that, all the traffic was type-in traffic (I later sold all the type-ins) and the high conversions were largely down to the fact that we only ever gave away 10 galleries a day and no-one could leave the site unless it was through a sponsor.
Even with the banners and other gifs, the index is still only 50k which is pretty damn good bandwidth wise.