An enterprising XDA member was able to yank the HTC One's default Sense 5 wallpapers while handling the device at an HTC event in Italy, and he's uploaded the files so everyone can enjoy them. There's 18 in total, and they range from the abstract to minimal, with a couple artsy black and whites thrown in for good measure.
To use them, visit the source link below and download the rar file to your computer. Extract it and copy the files to your device storage, and set using the normal tools or a "helper" app like Image 2 Wallpaper from Google Play. There is some very nice pictures here, and it's well worth a look.