Modify what you have so that the math fits together.
Backdrop doods are 6 frames.
Pogo guy was 30 frames. --> changed to 18, a multiple of 6
Backdrop doods are 300 pixels wide. --> changed to 288, a multiple of 6 and 18
At 1 pixel per frame scroll speed, backdrop will wrap in 288 frames, same number as pixel width.
Now that all the math is right do the scrolling motion.
Place a duplicate of the backdrop next to itself.
Backdrop1.x = 0
Backdrop2.x = 288
Now move both backdrops 1 pixel per frame until Backdrop2 replaces Backdrop1.
Keep in mind the journey for B2 to replace B1 will take 1 more frame than the width.
The last and first frames will be duplicates, so delete the last frame.
I used Flash to created the scrolling with a tween, much faster than moving the backdrop per frame by hand.
Export pngs, import into GraphicsGale as animation, check the pixels, save as gif.
Messed with the pogo guy.
Try to focus on improving his motion
Make him shoot up, slow, hang at the peak, slow, drop down, compress, loop.
Didn't change any of the drawings, only the positions and frame count to adjust the motion.
Having the frame multiple limit in place will help you make choices.
The colors could be improved.
There are some clarity issues.
Here's the edited images: