every directory usually has the files 'clear.gif' and 'blank.gif' added; these are completely transparent or blank images for your use. simply type clear.gif or blank.gif into an image field to use.
most of the pages also have version without the editing pills, at 'sketch.cgi' instead of 'sketchzilla.cgi' in each directory.
one use of this feature is that you can edit with sketchzilla, then save it as a page to upload somewhere else that can't be edited.
here's a great one used on the site by a random user, which allows you to customize fields on the site from remote locations... allows for larger field sizes as well:
<form action="http://www.sketchzilla.com/sketchzilla/story1title.cgi" method="post"> <input type=hidden name="text" value="___your message here___"> <input type="submit" name="submit" value="Sketchzilla"> </form>
copy and paste this into any large field at sketchzilla and edit away.
in the 'form action' field, put in the address of any sketchzilla field script you wish to edit (click a pill somewhere and 'view source' to get .cgi address)
form 'name=' has to match the corresponding name for the .cgi address field you found in the previous step
form 'value=' can be anything you want. in this case, its text intended for a text field. this could be an image url for an image field, a color value for a color field, etc.
advanced: how to enter more characters into a restricted field size
save a copy of the html page for the field you wish to change.
open the html page in a text or html editor.
inside the <head> html tag, add a <base href=> tag that has the root directory name of the page. for the example above, the tag would read <base href=http://www.sketchzilla.com/sketch2/>.
customize the <input type=> tag. size= and maxlength= can be adjusted. text fields can have a maximum of 255 characters. for more characters, try changing the html to a text area.
save the page and open it in a browser; it will work with the server scripts right from your machine. you'll be able to add as many characters as you'd specified in your customized form.
* the key is to basically send field input to the <form action=> .cgi address from the html input page you're selecting. make sure you get the variable names right as well.