I wish that bookmarks could be given icons. There not only much easier to locate but would put some in the bar with out any text to save space.

For Example: I have an icon-only bookmark in the bar for a link to Firstlook (a meta dictionary) the site provides a bookmark that will automatically search for any selected word when clicked but then there is no icon.

I don't think there's a way. In order to use the favicon, you need a<link ...> tag in your html page.

There might be a way to set it when the API is released however.

EDIT:

If you really need it.. this tutorial might help you http://www.tech-recipes.com/rx/3032/...bookmarks_bar/
But i'm not even sure this applies to bookmarklet.

This is the kind of feature that you could suggest to Chrome.

I figured out a way to put a icon in javascripted bookmark using SQLite Database Browser. It uses the same method found at tech-recipes.com but with a few... more steps.
It simply requires adding another row in your history with the bookmarklet's javascript as the URL, so it knows what icon to use.

step-by-step

1) Download SQLite Database Browser
2) Copy this entire post to a notepad or take a screenshot, so you'll have these instructions...
3) Close Chrome (all instances... very important)
4) Run SQLite Database Browser after extracting it from the zip
5) Open the filename called "History" found in the following folder (except replace deepdvd with your username

C:\Users\deepdvd\AppData\Local\Google\Chrome\User Data\Default

6) Go to your Execute SQL tab
7) put the following line as the SQL string:

insert into urls values (9999,'temporary string','Up',1,1,'12911564324482627',0,178)

8) click Execute query
9) Go to the Browse Data tab
10) Choose the table "urls" in the dropdown
11) scroll to the bottom where you will modify the line with the id 9999
12) change (by double clicking the field) the "id" 9999 to be the next sequential number after the one above it if you want... not required
13) THIS LINE IS THE KEY PART... change the "url" to be your bookmarklet javascript... the same as your bookmark URL. An example is the following line which is one of my favorite bookmarklets that lets you goes up one level in your current URL:

javascript:void(location.href=location.href.substring(0,location.href.substring(0,location.href.leng th-1).lastIndexOf('/')+1))

14) change your "title" if you want. You can change this later in Chrome if you want. I actually just want an icon, so I remove it completely. I love that Chrome bookmarks don't require a title. Change any other columns if you want, but it's unnecessary

15) change your "favicon_id" (far right column) to be the one you want from another URL in your history (same method as the tech-recipes link)

16) Hit the disk icon to save or close SQLite and confirm that you want to save.
17) Open Chrome and see your results! (assuming you have the bookmarklet already in there)