After a thousand years, about the only things made by man during a technological age - would be in space. And even if solar winds eradicate our footprints in the Lunar soil, our little buggy will still be there. Not to mention that we've certainly left enough debris and satellites in orbit. After all that time there might still be some that haven't yet fallen back into the atmosphere. Ooh, and maybe that could be a plot point. A world controlled by a few who hold all knowledge of history and science to themselves, find their control threatened when a satellite crashes back to Earth. And perhaps its discovered by a 'monk,' or other learned individual who has a window to the past, with all its wonders and terrors, opened up to him...
I suggest you read the book Anthem by Ayn Rand, it basically covers your topic and I thought it was a well written book, easy to read, too, and with good twists in the plot. What is well covered in particular is the world-after-the-modern-age stuff - it's depicted so well you feel depressed by the overall authenticity.
I read through this entire thread, waiting for somebody else to mention Riddley Walker by Russell Hoban. Nobody did, so I will. This is EXACTLY the scenario Hoban writes about, and in a most eye-opening way. It's not an easy read, but the payoff near the end is SO worth it! I do like Thom's suggestion of strange thingies falling out of the sky, too. Wonderful idea for a story.
A thousand years? I would assume most roads to be overgrown and pretty much every bridge to have collapsed with the ruins being pretty green as well. The base of large buildings might be intact and home to some interesting ecosystems of animals and plants growing in the concrete and adapting to hunt in a rigid environment.
What is your purpose in setting the story in the distant low tech future? Is it a part of the plot? I would imagine if it was, you could use the needs of your plot to guide how you construct your setting.
I think most people here are too pessimistic. 1000 years is not a very long time. You would find human artifacts, lots. There is no way to systematically destroy all the millions of artifacts we produce every day so completely that no trace will ever be found. They're still digging up Roman coins, sword-blades, even (in rare circumstances) wooden artifacts and clothes. A desktop computer thrown into a swamp in the year 2013 will still look pretty much like a desktop computer in 3013 (but good luck turning it on!).
