It's a little hard for me to understand what you are asking for. You want an image that, when you zoom in on it, it increases its resolution (so you don't see chunky pixels)?
In that case, it sounds like you're looking for vector format images. Any raster format (JPG, PNG, etc.) will have a fixed resolution. When you zoom in, a single data point (pixel) of the image will grow to fit multiple pixels on the screen. A vector format (EPS, PDF, etc.) stores data on the "objects" within the image, rather than the pixels themselves. Thus, when you zoom in on a line, it recalculates what the line should look like on-screen, and will display it smoothly.