painting your own insignias

I can't see the pic, but by the link i am guessing you mean the Elephant insignia. Not sure what scale your doing, but is there any reason you can't get decals for that.

1:35 scale, The decal kit I got with my kit doesn't contain this decal and I can't find any other decal sets that incluse this in the correct scale. That and I want a challenge.

I think I would save that image on my computer, then using a favorite image editing program rescale it to the appropriate size.   Print the image onto clear decal film.   I've used the Testors decal making set.   Seal, then apply the decal as normal.  

Also can't see the image...but I would suggest painting it on a piece of clear decal instead of on the model. That way you can play with the size and brushwork until you've got something you're happy with, instead of committing yourself by painting directly on the model you've worked so hard on.

If you don't have (or want to buy) clear decal paper, you can often find useable 'scrap' areas on kit sheets...such as the clear film areas at the center of zeros, or 'spaces' between letters.

You can also practice on stuff like shiny-coated cardboard if you're trying out paint consistency and how much to thin, or extra details that you might want to add.

It's not that tough with a little practice. Good luck.

The Schwere Panzer Abteilungs are immensely popular subjects for modelers and there's a lot of different decal companies catering to that market. Modify your search parameters a bit and you're sure to find decal sheets from manufacturers like Archer Fine Transfers, Alliance Modelworks, Star Decals, and others still. Most will include the 502"s mammoth as part of an assortment which will normally include insignia from a variety of the Abteilungs. 

If painting the mammoth on is really what you have your heart set on, there are also stencils available on the market which allow you to airbrush on the insignia. Pretty simple solution, really, because it takes care most of the work for you.