I'm not sure what do you mean by "sidebar", but I believe most of what you are looking for is found in the (you need an account to see links)
For example, to change and play with the userbars you have, you can check (you need an account to see links). Don't worry if you don't have too many of them! It's never late to start collecting, and you are right in time for some spooky seasonal ones! You can read more about userbars and how to get them (you need an account to see links).
As for a signature, you can edit it (you need an account to see links). If you want to have some custom made pics to put there, a lot of people in our community offer to make these! You can find most of their threads in the (you need an account to see links). If you are into old-school looking signature, I'm open for requests! Have a look in (you need an account to see links) for more details