how to add images getting from server to google map android as a marker?

Question 1

here is the complete solution. create Marker like this

Marker source = mMap.addMarker(
                   new MarkerOptions()
        .position( 
            new LatLng(
                Double.parseDouble(info.getLatitude()), 
                Double.parseDouble(info.getLongitude())))
        .title(info.getBankName())
        .snippet(info.getBankAddress())    
        .icon(BitmapDescriptorFactory.fromResource(getBitmap(url,this)))); //call getbitmap() method to download image from url

Download bitmap from url

add method getBitmap and decode method in your project(for ex. util class or common function)

public static Bitmap getBitmap(String url,Context context) 
    {
        FileCache fileCache=new FileCache(context);
        MemoryCache memoryCache=new MemoryCache();
        File f=fileCache.getFile(url);
        //from SD cache
        //CHECK : if trying to decode file which not exist in cache return null
        Bitmap b = decodeFile(f);
        if(b!=null)
            return b;
        // Download image file from web
        try {
            Bitmap bitmap=null;
            URL imageUrl = new URL(url);
            HttpURLConnection conn = (HttpURLConnection)imageUrl.openConnection();
            conn.setConnectTimeout(30000);
            conn.setReadTimeout(30000);
            conn.setInstanceFollowRedirects(true);
            InputStream is=conn.getInputStream();
            // Constructs a new FileOutputStream that writes to file
            // if file not exist then it will create file
            OutputStream os = new FileOutputStream(f);
            // See Utils class CopyStream method
            // It will each pixel from input stream and
            // write pixels to output stream (file)
            Utils.CopyStream(is, os);
            os.close();
            conn.disconnect();
            //Now file created and going to resize file with defined height
            // Decodes image and scales it to reduce memory consumption
            b = decodeFile(f);
            return bitmap;

        } catch (Throwable ex){
            ex.printStackTrace();
            if(ex instanceof OutOfMemoryError)
                memoryCache.clear();
            return null;
        }
    }

    //Decodes image and scales it to reduce memory consumption
    private static Bitmap decodeFile(File f){

        try {
            //Decode image size
            BitmapFactory.Options o = new BitmapFactory.Options();
            o.inJustDecodeBounds = true;
            FileInputStream stream1=new FileInputStream(f);
            BitmapFactory.decodeStream(stream1,null,o);
            stream1.close();
            //Find the correct scale value. It should be the power of 2.
            // Set width/height of recreated image
            final int REQUIRED_SIZE=85;
            int width_tmp=o.outWidth, height_tmp=o.outHeight;
            int scale=1;
            while(true){
                if(width_tmp/2<REQUIRED_SIZE || height_tmp/2<REQUIRED_SIZE)
                    break;
                width_tmp/=2;
                height_tmp/=2;
                scale*=2;
            }

            //decode with current scale values
            BitmapFactory.Options o2 = new BitmapFactory.Options();
            o2.inSampleSize=scale;
            FileInputStream stream2=new FileInputStream(f);
            Bitmap bitmap=BitmapFactory.decodeStream(stream2, null, o2);
            stream2.close();
            return bitmap;

        } catch (FileNotFoundException e) {
        } 
        catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }

Question 2

Firstly, get the image from URL.

Secondly, after getting the image you can use overlay for adding custom marker on map.