If you want to receive an image from the server (like a PNG file) with Java ME you should use this code:
// This snippet only works if the server send the image length
HttpConnection c = (HttpConnection) Connector.open("http://www.mydomain.com/myimage.png");
DataInputStream response = new DataInput(c.openInputStream());
byte[] receivedImage = new byte[c.getLength()];
response.readFully(receivedImage);
response.close();
// We have now the image in a byte array.
// We have to transform it in a LCUI Image object
Image im;
im = Image.createImage(receivedImage, 0, receivedImage.length);
// Now you can use this image to draw it on Canvas or store in RMS