I don't quite get it. Will the solution of the picture increase forever and everyone visiting the site or is it just for my web-session on your page?
Visitors pay to increase the resolution for everyone.
So if you upload a photo and set the price to 5BTC, it will be shown at the maximum resolution when the total amount of BTC paid to the picture's address reaches 5BTC.
For example you upload a picture that is 2000x1000 pixels. You set the price to 5BTC and the initial resolution to 100 (which is the default).
Initially the picture's resolution will be 200x100 (0BTC paid)
For 2.5BTC paid the resolution will be 1100x550 (that is the smallest size will be halfway between 100 and 1000 just like 2.5BTC is halfway to 1BTC).
For 5BTC the resolution will reach 2000x1000.
Additionally the quality of the served JPG file will increase. In the end the quality setting will be 100% which is almost lossless.