I agree that pngs are better and it should be changed. I guess we need to hear from rarebit as to why it never was.
There is one thing to be said about limiting size as it forces the author to concentrate on topic to make the most of his limits. Does it need to be a 256k jpg? I doubt it.
As I think about it, such a small file size, or any reasonable file size for that matter, is an artificial and arbitrary parameter with no true positive bearing on an artist’s ability, much less the final render.
If anything, an artist might be more inclined to develop fewer fine details and/or textures in an entry because those things will only be decimated by necessarily higher compression or rendered virtually imperceptible by the necessity of a smaller render in an attempt to adhere to the posted K limit.
The chosen topics, time constraints of the challenge, along with the usage of Blender governing Pure/Open status, are helpful and sufficient limits which can push artists forward in this challenge without demanding them to sacrifice quality.
Speaking of quality, one of the lasting motivators in this challenge is the consistently excellent work of the participants. I’m always amazed and humbled by what people post. It’s really an inspirational challenge!
RobertT
Oops double post. Anyone know how to delete a post? 
the forum itself will turn your png into a jpeg if it’s too big, no way around that. Seems like anything around 680 by 680 will be accepted as is with no thumbnail or modification. At 800, it will still be a png, but thumbnailed. It’s bad enough that facebook JPegs everything I post ><
Uploaded files hosted directly in this forum are understandably limited in size due to overall bandwidth considerations for the website owners.
If personal or third party image hosting is available, then that might be a better option for some artists.
Monthly bandwidth limits do kick in elsewhere as well, especially where cheap or free image hosts are concerned.
With that in mind, for simplicity’s sake, I think we can do without the 250k rule so challenge participants can just do whatever is best for them in light of their present bandwidth / hosting circumstances, be it whatever inline forum images might be limited to here or whatever one’s own Web/image host establishes as upper limits for file sizes and monthly byte transfers.
Also, remote as it is, I would not want someone’s otherwise excellent image to be removed from consideration by a challenge voter simply because the render rang in at 251k
RobertT
My vote goes to Enos Shenk. Nice textures and overall atmosphere.
Some nice entries this time around.
I would agree on removing/increasing the size limitation.
Drive size have increased substantially over the last 10 years or so;
(there may be still some bandwidth / hosting issues though??)
would we tell artists/painters that you’re only allowed to use a 1 square foot canvas?
Again I would wait for rarebit as for some reason it hasn’t changed. It may have been overlooked. Honestly, being this is weekend challenge, I would favor a limit. fcharr brought up some thumbnailimg that happens in this site naturally. Maybe that should be the limit, or at least the suggested limit knowing your work might get distorted anyway beyond your control. No use making something 3k pixels tall and wide if it will get shrunk to a third its size.
I guess we don’t really need that 250K limit anymore. However, I still think that it is a good idea to keep the file size down if possible. (So far I haven’t had to many problems with the current limit - and after all (depending on the image, settings and the software used for compression) JPEG isn’t bad at all.)
On the one hand it is unnecessary to destroy an image only to match an ancient size limit - but on the other hand a 10MB BMP file isn’t something someone with a limited bandwidth or traffic (e.g. on a mobile phone) will be too happy about.
Let’s just leave it to common sense. On that note: As RobertT said before, I don’t think the file size is something that should keep an entry from winning.
Btw.: the Poll is working fine now. thx rarebit (Challenge #645 Voting OPEN)
If someone actually uploaded a 10mb BMP they should win some kind of prize. I’d chip in to buy them a rubber chicken or something.
File size is probably just a holdover from the old days when folks other than grandparents used dialup. I guess we’d have to dig up TheEth to confirm though.
Sadly there was never a high res version of " yellow cube with interesting lighting ". ( if you haven’t been around since the caveman times, you won’t get the joke )
I had to look that up. Post is there with no pics. What do you think, good contest idea?
haha. good find Robert, and the colossal cube is hilarious. lens flare added in pp of course.