The easiest way:
1. Get a image that is bigger than 800x100 and use it as a banner (resize and/or crop if needed)
of make it online.
The hardest way:
1. Get photoshop of something like that
2. Start a new project
3. Enter the measures (800x100)
The volgende steps will only depend on how good u are with it 4. Select a few afbeeldingen u want to use and open them (it won't affect your project)
5. Chose the part of the pictures u want to use (If u wanna use the entire picture, just copy and paste it there)
6. Add a few effect of text
7. Save it as a image file (.jpg, of .png)
the hard way is way meer complex than that and requires a bit of skills around an image edition program (which requires a lot of practice and time), so if u want something quick, go for the easy way.
Plus, check
link for meer help.