To my eye it just looks like what I'd expect at that frame rate. You want it smoother, do the project at 720p/60. The extra 30 fps should do the trick.
You could also try adding just a touch of blur to the image. I know that may not sound like what you want, but at least try it. Don't go overboard with the blur though!!!
If your project is interlaced go to the Field Options of the still and set it to Always Deinterlace or Flicker Removal.
Jim, the project has all 29.97 video files so I didn't want to fool with turning it into a 60 fps proj, although it might have helped for that particular tif clip's flicker.
ExactImage, I tried the blur at various setting but it still had the flicker.
Ann, I tried both settings in Field Options but it looked the same.
The solution for this is that I halved the width of the tif..but crammed all the image info, as much as I could with overlaps and some mural images taken out, into half the width.
So half(6000px) of the original tif width takes the same amout of time that the former(12,000px) 2X width tif took to scroll and the flickering is greatly reduced..
I had a similar problem with a timeline involving high-res stills. I turned off GPU acceleration for rendering (File > Project Settings > General...) and the flickering went away.
The render takes twice as long on my MBP, but at least it works. There are similar complaints on the Creative Cow forums. Looks like this is a known problem with GPU rendering.
(EDIT: It looks like the flickering happens using the OpenCL renderer, but not the CUDA renderer. And CUDA seems to be faster anyway. This seems like an issue where YMMV, so throw a bunch of spaghetti at the wall and see what sticks.)