The address to the template's top_image.jpg should be like this:
http://www.your-site.com/phpBB/template ... _image.jpg
It doesn't matter what you call your forum folder, but the C in Conundrum must be a capital C. And there should only be one Conundrum folder. Sometimes i have seen it uploaded like ...templates/Conundrum/Conundrum.. which is ofcourse wrong.
Once you have this correct, check to see if the theme_info.cfg file have been uploaded. It's an important file, as it tells phpBB about the name of the template. If you open it, check to see that all the lines starts with $Conundrum. Also check to see if the first line have the template_name set to Conundrum. (About style_name: If you want your visitors to see another name than Conundrum in their signing-up/profile window, change the name in the second line but not the first).
If you've done all this and it still doesn't work, i would say it's probably the ftp program that did something it shouldn't do. Try to see if the files in the folder all have the permission of 644.
I've been to hiphop concert last night and my head is in a very unstable condition right now but (at the moment) i think these are the only things that could have gone wrong. 8)