Yes, you can. Since our backup is based on rsync, you can use rsync filters to exclude files and directories.
To exclude a directory, place a file called .rsync-filter in the directory, with the following contents:
+ .rsync-filter - *
If you need to exclude certain files, for example compressed logs from /var/log, place a file called .rsync-filter in /var/log:
You can find more examples in the rsync manpage, under the FILTER RULES section.