If possible, use filenames that are meaningful. Digital cameras number images as IMG5023.JPG, which does not really suggest what is in the picture. When you include images in a web page, it helps to use filenames that are meaningful, such as tom_and_jerry.jpg.
It is a pain to rename files. This is especially the case if an image is shared among different existing HTML documents. However, most servers permit the use of “links”. A physical file in the file system can be aliased by different filenames in different folders using “links”. Note that a link is not a Windows shortcut.
If you are interested, look up the terms “soft link”, “hard link” and “symlink”. Unix-type servers support both soft links (also known as sym links) and hard links. NT-based (Windows server 2003 and variants) also support hard links. You do need to make sure your authoring software also understands the concept of links.
Using links, you can have a master folder that contains the original meaningless filename. Then, you can create meaningful aliases (possibly in other folders). HTML documents refer to the meaningful aliases.