If you have PS you will have no problems adjusting scaling. PS will handle all the scaling but you will have to cut and paste by areas and scale floors separately from walls. PS will handle all this, however it is not a trivial process. You say your miniatures are too small for chunky. What scale are we talking about here?

Chunky dungeons are predicated on the concept of a 1.5 x 1.5 tile. So a 1X2 tile arrangement is 1.5" wide by 3" long. A 2x2 is 3" x 3", etc. Walls must therefore fit in a 1.5" wide.

Floor scaling in PS is rather simple. If I recall correctly Chunky floor tiles are 200dpi. So to very easily scale down, you take a 200dpi tile and dump it in a 300dpi frame. Instant scaling. You just reduced your horizontal and vertical size by 50%. After you do this you will notice what the real problem is... 1" x 1" tiles are too small for anything worthwhile. So you'll probably end up going to a bigger tile that is 2" x 2". To do this, simply scale the tiles up by 100% after you've scaled them down by 50%.

I know, confusing, but like I said the work involved is anything but trivial.

Walls are even more confusing. Each wall is .75" wide and placed on a 1.5" tile. So scaling those requires you to know what you want to do before you start because you probably don't want to reduce the walls in height.

You could easily increase the size of the base of the wall on each side by .25". That will keep your wall as .75" wide on a 2" tile, which fits with our other "bigger" tiles. Then again you could reduce both the width of the wall to .5" and the tile to 1". Making the whole wall fit on a 1" wide tile.

That does not take care of the current legth of the walls which is 3". You could decide to make it shorter to 2" or longer to 4".

See what I mean? Walls have to be designed from the ground up based on how you want your floor tiles to fit.

If you have specific questions I can help you but you probably need to decide how you want to scale it.