Installing firmware onto a wrt54g using tftp

I have been having some problems trying to reflash my old linksys router using tftp. I wanted to try out dd-wrt but could not get the firmare to load.

First off I was getting an error 4 "transfer canceled" which turned out to be that the image was too big so I tried a smaller one but then I kept getting the error 3 "code pattern incorrect" turns out that the bin image that I had downloaded was gzipped but with no .gz extension so after unzipping it I was off. Loaded in the small openwrt version which then let me load the dd-wrt that I wanted throught the web interface.