How to implement a set of images / diagrams in a website?
To answer your question, I think it depends on how you plan to use those images ...

Option 1: use individual images to beef up specific content pages

In this case you just upload those images to a folder such as sites/default/files, and then you could just use them (refer to them) with a typical img tag. To make sure that these images will actually also be rendered (when viewing the page), make sure that the "text format" used in the node does allow the img-tag. Typically for a node using the "Filtered HTML", it could well be that the img-tag is not allowed (yet) as one of the available HTML tags. In that case, your HTML code does include an 'img" tag, but when viewing the saved node the image is not rendered (visible). To resolve it, within admin you must enter the img-tag as one of the allowed HTML tags for the text format used in the node.

Option 2: visualize them in the format of a Gallery

Talking Drupal #083 is a great podcast about this topic, and includes a lot of recommended modules in this areas. Just to mention a few of them (mentioned on the linked page):


  
  Gallery formatter - https://www.drupal.org/project/galleryformatter
  Views Slideshow - https://www.drupal.org/project/views_slideshow
  Flexslider - https://www.drupal.org/project/flexslider
  Node Gallery - https://www.drupal.org/project/node_gallery
  Multiupload  Filefield Widget - https://www.drupal.org/project/multiupload_filefield_widget
  Multiupload Imagefield Widget - https://www.drupal.org/project/multiupload_imagefield_widget
  Field Focus - www.drupal.org/project/imagefield_focus
  pl upload - https://www.drupal.org/project/plupload