I have a astro hog kit on the shelf, I like the look of it myself,so if you like that build it, it's a bit bigger than what you have done.
If you want a bit more of a challenge, a WW1 BUSA bipe like the 1/6 sopwith pup will test you a little more, but certainly not hard to build.
I have the 1/4 and I think they build pretty much the same, you will find 1/4 will be more stable in the air though.