Most of these answers are stating that if you save it in a different file format, you can reduce the size.
This is incorrect. Different file formats may make your image smaller, of course, but it all depends on the image itself as well as the particular compression and optimization settings you are using for each image.
So, yes, certainly try saving your image as a JPG or GIF and see if it helps, but it's no guarantee it will be any smaller.
As for your current image being 1k, note that that is already really small. There are also limits to how small an image can get that are somewhat out of your control:
- minimum hard drive sector size. The image the size is reported at on your hard drive may actually be bigger than the image itself. This is due to the fact that the larger the hard drive, the larger the minimum sector size is. For really small files, you'll note that moving them to a smaller sized hard drive actually will report a smaller file size. This isn't relevant to internet bandwidth, of course
- file meta data. Most all files have meta data. This is data not directly related to the image's look, but is ancillary data that the browser or file system may or may not use (such as a file icon). You can use software to modify or strip this meta data away.
As for your concern, that's not entirely clear. Are these all separate images, or just one image? If it's just one image, then in terms of bandwidth, it's moot, as only one copy of the image needs to be downloaded from the server for total bandwidth usage of 1k.
If these are all different images, then you're likely better off using sprites. This is where you take all of your individual small images and place them into one large image. You then use CSS to 'crop' each individual image out of the sprite on the browser-side.
While this may not reduce the total amount of files size, it drastically reduces the amount of server requests which can greatly reduce download speeds.