How to make images tiny, less than 24x24

I'd like to a tiny image/symbol in narrow columns (within a table) to display an activity against a week of the year (i.e. I will have 52 columns).  The smallest I seem to be able to make the image is 24 x 24 which does not allow me to reduce the width of the column enough.  The images always 'centre' and expand to be 24x24. 

A work around is for me to find a 'left aligned' image - with white space to the right.  Are there any other solutions?  I really just want a small symbol against a week number, using "*" does not look great aesthetically. 

Thanks for your help