You should never give your pictures away for free.
That resembles a buy out, you image is spread all over, and as you have noticed you may get a download or two, or even 20.
But that amount does not compare to putting  an image in the trash or the feel free to copy bin.
By giving away you undermine yourself, the agency and other agencies.
Luring you into do it is a competitive advantage for the agency on behalf of you and other agencies.
Do not do it.

Also if the agency wants to do fancy free marketing, it can do it out of the commission it gets.
Thats the purpose of agencies, they get shares because they market.

Its their meaning of life.
Your meaning of life is to produce content.

I wouldn't do it - even though they only give away a very small size.

They pitch it as getting you exposure but I think that may be overstating the case a bit. It helps the site to have some freebies - perhaps.

I have only done free image of the week at a few sites (iStock never took any of the things I offered) as it seems that a 1-3 week giveaway as a way to help a site that it truly your partner (remember those days??) is a reasonable thing to do even if it doesn't boost your sales. But that's one at a time rather than the pool of freebies.

I recall selling an image at one agency while it was a freebie that week at another - I don't think regular buyers go looking for freebies - so in general I don't think it hurts much.

And as far as doing anything to help 123RF, even if I thought it would help them I'd stay away as they've been so anti-contributor as they've walked away from the 50/50 split to a "what did you do for me last month" model of royalty levels.

     Just  2  for  30  days  so  i  gave  it  a  chance.  Did  the  golf  cart  sale  come  from  the  freebie  altough  it  was  a  different  pic?  I  won't  do  it  again  anytime  soon  unless  i  start  getting  more  DL's.