There are a few mods which add defined musculature to the girl's arms (
example). If you'd like to see larger and/or softer then you should provide a few
reference images which depict the desired visual effect. Remember that arms need to bend, so try to get a few different side-view shots.
If you're really eager to see this happen then you could draw, trace, or crop-copy-paste the new artwork onto the
SVG or
PSD template files. A Flash modder can then directly import your work and create a working SWF file in a few minutes.
Please remember that clothes will usually
not fit onto a modded body shape. If you want to preserve compatibility with specific items (such as the vanilla T-Shirt or whatever) then you should talk to the modder about it. If you're willing to leave the girl's arms bare then that's fine; no extra work is needed.
You've posted this thread in the vanilla
requests section. Modders sometimes employ
more advanced scripting in order to achieve more complex results (such as depicting the "thick" version when the girl's arms are held behind her back, or including all four skin tones in one SWF file). We can move the thread to the
Loader requests area if you'd like to see such features, or we can leave the thread here if you'd prefer a vanilla mod (for compatibility reasons). Either way, please
edit your first post to include a description of what you're looking for (specific features, custom skin tones, vanilla compatibility, etc).