Alright, let me try and be of aid here. I'm going to walk myself through the process as we go, so that I don't skip anything.
Establishing the basic grid
1) Open Excel
2) Resize the boxes to the correct size (I think you know how)
3) Highlight the section of boxes that you are going to use...
4) right click in the area, click [Format Cells], then go to the border tab and give all of the boxes a full border
Adding Images
1) You say you want some 'cool icons', and well, the way I go about doing this is to insert images.
2) Use the insert tab from the dropdown menu, select picture, then select "from file" and insert whatever pictures you want to use for icons.
How to post a map
1) Highlight your map, press control-C
2) Open Paint (or whatever graphics program you have available), and press control-V.
3) Save the file, and post it as an attachment to the boards.
Drawing Toolbar
1) One of the tools I use quite often is the drawing toolbar, it may be visible or hidden on your excel settings.
2) Go to the View section of the dropdown menu.
3) Open the toolbars section, and activate your drawing toolbar
4) There are a number of things to play around with here, they will all help in editing a map.