Is there any tips for newbies to creating own objects ?
1) Don't just plop whatever image you find on the internet onto your map (the map background included). First check out how big (kilo/mega-bytes) it is, then if too big, use a tool (like GIMP or Tokentool) to process that image and make it lighter weight. I try to keep my token images to 250x250 pixels -ish.
2) There are tons of images floating out in the Web. Just remember that if you use an image, you may not have rights to that image. Generally speaking you should be able to use it for your own private use, but if you share what you have done with this forum, make sure you have rights to the images you share.