Nanabu - I know exactly how you feel mate.
I was getting seriously bogged down with the repetitiveness of it all, then my PS3 broke. After about a month I managed to get it fixed, and I must admit the break from shooting and editing did me a world of good.
I've found just recently that I'm inspired by other people's shots more and more including your good self. The talent on here has shot through the roof just recently - the editing on a lot of shots is top notch and I've found myself trying to imitate some peoples' styles. Also new members have injected a bit of life into the community - Leeislee amongst others.
But yes - I agree the tracks, cars and locations are getting very tiresome for me too. At the end of the day, GT5 is now quite an old game, and GT6 cannot come quick enough for me. I only hope the new release rectifies some of the more annoying elements of GT5. Stuff like the clunky menu system (why not just have a 'home' button on every screen? Or something like 'Little Big Planet' where a button activates a little console so you can immediately access different sections?).
I also hope the camera is tweaked to include new features like saving your last settings (I hate having to switch ratios and modes ALL THE TIME!). Perhaps a true free-roaming camera?
All this doesn't inspire me to fire up the game and get shooting anymore. Which is a shame. I'm always of the mindset of 'Oh, dya know what - I can't be bothered'...
All I can say is don't feel that you have to come up with new and exciting shots every few days. I certainly don't - I only post when I feel 'in the mood' these days. Which I've found is now getting less and less...
It'd be a shame to lose ya - perhaps a few weeks off is needed?