Venue - Theme settings - Customize your store's checkout design

All stores on the Shopify platform use the same default checkout page design. Using the Theme editor you can customize and personalize the look and feel of your checkout pages to match the style of the rest of your site.

These are the main elements you can customize:

• Banner - this is a slim background image in the top of the checkout pages.
• Logo - use a custom logo
• Position - move the logo left, right or centered.
• Logo size - small, medium or large
• Main content area - put a repeating image or color behind the forms that your customers fill in.
• Forms fields - if using a background image, it can look quite stylish to make the form fields transparent.
• Order summary area - put a repeating image or color behind the order summary area.
• Colors - Change the accent, button and error message colors.

Pro tip: You can fine tune the checkout pages even more from the Shopify admin area. 

Here is Shopify's help article which outlines the ways in which you can customise the style of your checkout.