You can customize the design of your tickets per event, but in Settings - Ticketing - Design, you can set the default settings. This only affects the downloadable PDFs of tickets, so not the mobile tickets or the tickets added to the Apple/Google Wallet.
Logo
Your logo can only be added in the default settings. Go to Settings - Ticketing - Design to upload or change your logo. This image will appear on every ticket PDF.
Ticket image
You can also add an image to the ticket PDF. For the best results:
Upload a square image. (1:1 dimension)
Upload a .jpg or .png file. (No PDFs)
Upload an image with a print resolution (300 dpi).
Maximum file size is 0.8 MB (800 KB).
Don't use uncommon characters in the title of the file. This can lead to errors.
This setting can also be customized per event in the Tickets tab of the event.
Ticket text
There's also space to add text to the ticket PDF. Here you can put more information for your ticket buyers. For example 'No need to print your ticket, you can show it on your phone.'.
This setting can also be customized per event in the Tickets tab of the event.
Spaces
Spaces belong to a location, which can be set in the Main tab of an event. Some locations might have different spaces where events can take place, for example Concert Hall 1 and Concert Hall 2. In this setting you can decide whether or not you want this to be shown on the ticket. This is a global setting and can't be set per event.
Sample ticket
With the Download button under Sample ticket, you can download a preview of the ticket PDF.
The language on the ticket depends on the language of the ticket buyer's shop (which is dependent on their browser's or system's language settings).