Q: Can I check if the dimensions for the event page banner image? The guideline I see is 430px x 1000px, but the image element doesn't show entirely on my desktop screen (21') 

A: The image guideline 400px width is so that the banner will fit in the banner space. 

For the height of image,  to have the optimal results, when designing the banner (or cropping the picture to be used for your banner), keep the key elements and most important items of your banner in the top 700 px of the image. 

For instance, in the example of the banner image, the key elements are kept in the top 700 px of the image, highlighted in red. 

Also, the banner image looks different on different screen display too, for example, if viewing original 100% display, the same event landing page on a desktop with screen display 21' will show more design element than a laptop 13'

13' screen

21' screen