Most registered word marks and trade names consist only of letters, but you can also use numbers in them.
For trade names, you can also add punctuation marks, for example . , - + and &.
Make sure that the name is still legible for others and that it can be pronounced. Some entrepreneurs add a huge number of punctuation marks to their trade name, for example ---- or &&&&. Or they wish to add special characters to their trade name, for example ^ * ~ or {}. Often, such additions are meant as 'decoration' and the trade name cannot be pronounced properly. Keep in mind that such additions are not protected by the Trade Name Act.
If you want to register your name as a trademark, all punctuation marks can be part of the trademark.