In your comments you mentioned that you are still new to wordpress, and I believe you don’t have a full understanding of the template hierarchy. Essentially, wordpress looks for certain templates depending on what post type is being displayed. And if it can’t find any, the last resort is always the index.php file. Here is a flowchart that demonstrates wordpress’ template hierarchy.
So, now you understand which template is being rendered and why, you may be able to figure out that the reason your images and short codes are not working are because you are using the_excerpt() to output your content. This function automatically removes all short codes and tags. More info on this function here (the wordpress codex).
You may want to create a new template file – perhaps page.php* (refer back to the template hierarchy and you will see that this is the top level generic static page template) and use the_content() inside your loop to echo the content.
* I’m assuming you’re displaying a static page, if not use the correct template for the post type you are trying to display.