What is the risk of using number in image style preset name (imagecache in D6) There is a message below the preset name to be written. It not suggest us to write number:

The name is used in URLs for generated images. Use only lowercase alphanumeric characters, underscores (_), and hyphens (-).


Sometime I need the name with number such as thumb90, profile100x150, etc.

I can see some developer also write number in the name field.

Even no problem so far, I need to know what actually the risk of using number together in the name.
I have never seen the term "alphanumeric" refer to anything other than a combination of letters and numbers.

Since the style name gets used in the URL, the restriction to "Use only lowercase alphanumeric characters, underscores (_), and hyphens (-)" likely has to do with avoiding any escaping issues with URLs and for portability across filesystems that may not support the full range of characters in filepaths.

Personally, I have never (nor have my clients) run into any issues with using numbers in image sytles, though as a best practice I lean towards using descriptive names for use, rather than size, in the sytle name.  So, I will try to use "thumbnail_square" instead of "thumbnail_90x90", in case I end up changing the size at some point.