I did mine using "The Gimp" and MS Paint, and then trial and error until I got an image that fit all the formats I care about on YouTube (mobile and PC). It was a bit of a pain but I got something I am happy with in the end. You may also want to see how it looks on your Facebook/Twitter accounts too before finalising an image so you can maintain a familiar branding across platforms.
Motorbikes are tough to use as they are not banner shape so are either too small in the centre or have the tops/bottoms sliced off.
YouTube banner size is as below:
Channel art looks different on desktop, mobile and TV displays – larger images may be cropped. For the best results on all devices, we recommend uploading one
2560 x 1440 px image.
- Minimum dimension for upload: 2048 x 1152 px.
- Minimum safe area for text and logos:1546 x 423 px. Larger images may get cropped on certain views or devices.
- Maximum width: 2560 x 423 px. This means that the "safe area" is always visible regardless of screen size. The areas to each side of the channel art are visible or cropped depending on browser size.
- File size: 4MB or smaller.
I have attached as a zip file the channel art template from YouTube which may help you (or may not).