My suggestion is complementary colors. I like the idea of a contest centered on color since it's open to all kinds of artists. I think that focusing on complementary colors specifically adds an element of challenge.

Try to keep in mind, when suggesting a topic:

i) Open to all genres of art. Not just photography.

ii) Add a short description (one or two lines is sufficient) , so 'we' know what the artistic aim/intention of the subject matter is.

iii) Try not to repeat previous topics.

OK, Master Les, LOL
Hopefully we follow the instructions ... LOL
Originally I have been for "Industrial" since we never got it, but on second thoughts I decided that the complementary colours provides for a broader scope of works and artists.
SAM

I'm going with complementary colours for three reasons, it's thoroughly inclusive, it's specific without being narrowing and it requires some technical thought, and thus invites the possibility of some skills/knowledge growth in those who enter the comp. It would probably help, in that respect if there was a way (I know there isn't) to get the "judges" weighing the entries based on actual complementary colour use. :)

Haven't voted as yet!!?  But [love Google!] here is a link to info on Complementary Colours... including double, split and double split complementary colours! This, I believe, really helps to get a good/interesting image!   :o)

That topper image in the link really appeals to me!  :o)

This just in for the Apophysians out there, on the note(s) of 'complementary colors':

"Creating and Saving Custom Gradient Packs in Apophysis"


Or..

Click here.

Things that are rusted is a great idea for the contest. Even if it does not win this time, it needs to have its place. Complimentary Colors appears to be winning this time around but I hope the rusted one will come back around.

My living room is a Double Splits complimentary, the walls Willow Green sort of green, very mellow, restful & Zen. The furniture is is kind pattern on pattern, but it's all very subtle & all pulled together by the color green. My couch has an invisible pattern of green on green & my chair has a paisley design that I love, but it's very subtle.


More importantly, my curtains are a deep earthen, purplish red to offset all the green. Actually I have Roman shades but whatever.

So that color wheel is my living room for sure.

Stan... and others... my mind? tells me that things that are rusty would not be excluded from the complementary colours... as a matter of fact it is... to me... the colour (rusty) of the fallen leaves that creates the WOW factor in that topper image of my link above.
I had Googled! Industrial Images but couldn't find any that would be allowed/wanted here, that I would want in my Screensaver Folder. I do love pictures of things that are rusty... have a number of them in my SF! :o)

I suggest Moving Subject. I think that it's a great challenge to get this kind of shot. And I know that fractal masters can create movement in there creation... Running, jumping, surfing, skating, driving, hiking, flying.... So much possibilities during summer !!!

Here is another link... Youtube 3 min.! Complementary Colour Wheel I am not pushing for anything here... I will not be participating this go-round. I was not certain I understood fully the concept of working with colours so I Googled it and then shared my findings. I use Youtube to get info re. different photography skills and decided to see if there was any info on Comp. Col. The above link is perhaps the most pertinent to this topic. As a matter of note only [if that means anything!]... I generally have a preference for the cameralabs tutorials!