Should I create and use different uploaded images with different resolutions and sizes for different products or just doing one with the best quality is fine? Let's say for example I want to make very large posters and also small cards or mousepads, with the same image. For the posters, I'd need a 200-300dpi image with about 6000 pixels width, which is not really necessary for the small mousepad. Should I have 2 images to be used as a source, one for each project/item or just the biggest/better one is fine?

My fear is that high quality images are usually big and there can be some cropping if used to make smaller products, hence uploading smaller versions for smaller products would be safer although it would waste server space.