I'd personally say - Watermark.
Use Photoshop or similar program, to create a watermark logo then set it as a patern on a transparent layer and set the patern to around 4-10% opacity.
Now really If I personally REALLY wanted to get the water mark of the fullsize image or whichever large size crop you use the water mark on, I could, but would it be woth my time, probably not; would the skaters, most tech people, or average joe know how to get the water mark off properly - no way.
Its a pretty simple process to get it off if you can replicate the watermark or get the opacity values used, but if you do some fancy stuff with applying overlayed gradients or render clouds to only effect the water mark layer, it would be a super pain to get it off.
Anyway, 50% crops with watermarks sounds reasonable to me with 6Mp or above, and if its 10Mp+, 33.3% Ccrops with watermarks.
As for uploading, Flickr! Easy to use, search etc. and its pretty well known.
They also do printing in the US, and have affiliates to do printing in other countries in the world too.
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