You can assign each square to a grid cell (of bigger size), and choose randomly its position within the cell, with margins. The spacing would be almost regular...

Hi PhiLho,

Interesting question. Obviously, with 23 items, you can't fill all the cells of a grid... You will have some holes. Or you have to make it a bit more irregular.
sqrt(23) ~= 4.8, so you can fit 4 or 5 items per row (or column) of the grid.
Not sure how a grid can be squarish with a 70x30 canvas, you have large margins by the sides?
Anyway, divide the dimension by 5, and you get the interval you need.

With 200 items, you have 14 or 15 items per row/column.

An idea of the algorithm is to compute the number of items per row (column, I won't repeat...). You iterate on the number of rows, and for each row, you draw a random number, say 14 or 15, or perhaps between 13 and 16 if you want more variations. You make a virtual grid for the row, as we discussed above: for each cell, you compute the center, and draw a little random variation (x/y) from this center to draw your item.
Repeat, and for the last row, use the remaining number of items to draw.

I hope my explanation isn't too confusing. The algorithm isn't really hard, but you have to be organized to code it.