Hello! beCounted does let you change the statistic(s) whenever you want to, so you could do so on a weekly basis. The statistic is a rate (# per year) that represents how quickly the counter should tick while the user stares at it.
For example, if there were 6,586,000 Apple computers shipped last year, entering that number will count the number of Apple computers shipped since you opened the web page, representing a naively forecasted quantity based on the previous year statistic.
That concept could be related to artwork sales, but you would have to sell a large quantity in order for the counter to tick within a reasonable wait for the user. It may be helpful to think about any large statistics that you could use.