When selecting a custom vinyl banner for any purpose you need to decide on a couple of really important things, people are very particular about the design they select and the material that would be used and even give time and attention to what the font size would be, but they should always give attention to the size of the banner, when we would mount it on a higher place we need it to be the perfect size, not too big and not too small and that is why these are standard sized, you have to consider the purpose of it, one of the most important advertising tips I got from an expert was to keep it simple when designing the banner, be it about the size or print you are going to select.
If you are going to use it indoors then you will to select a smaller size and use different set of colors but usually vinyl banners are meant to mounted outdoors and the reason why polyvinyl material is used because it is able to withstand harsh weather conditions but it is really important to get the size correct, getting the size correct does not only mean that you will be getting the aesthetics right as the message would be clearly visible from just the right distance but the printing technique and finish also has a lot do with the selection of size.
The designers are there to help us out with the orientation, it is completely our choice but we may not select the right type of color or design or even size but the experts know what would suit best in what sort of orientation and even if you have a very particular image of how your custom vinyl banner should look like you should still value what the experts recommend.