What format and size should images be?

Images specifications are as follows:

• Minimum image width is 600px.
• Maximum file size 1 MB.
• Please DO NOT use file mode CMYK.
• No blank spaces in file name. (EG: filename01.jpg NOT file name 01.jpg)
• No special characters in file name. DO NOT use: & / ? ! + . , # @ [ etc
• File name max 20-30 characters long.
• Don't upload .PDF, .docx or .bmp files.