Okay, going back and looking at your pics much closer (which were at weird angles) I can see that your vrm area has only one mosfet) this means that despite possibly saying socket 7 it’s actually for all intents and purposes a socket 5 (we may have noticed sooner with a good model number and good pics earlier on. Sorry)
Anyway, unless you come up with a powerleap adapter you are probably going to be stuck with limited options:
The best one that comes to mind is the pentium mmx overdrive 200mhz of which a few are on ebay at the moment. Though, at frankly dreamer prices.
Also, basically I think any winchip will work on this, including I believe a 266? (Would have to look it up and confirm 3-3.3.5vcore)
But that’s about it. You can forget properly running a pentium mmx on this board or most of the k6 lineup that doesn’t specifically list core voltage as over 3v (166, 200, 233 I think are the 3v models). (A k5 200 or lower should be good to go though.)
Last I looked there was a powerleap on ebay under “multimedia cpu upgrade” again though, dreamer pricing.
Your cheapest route to a faster system is a new board I’m sorry to say. But this isn’t the end of the line for this one, with a power leap style adapter you CAN probably run a k6-3+ 400 or a 233 mmx, or a cyrix mII at 233 (maybe even 266 with bf2 mod) or a tillamook at 266 (with chip mods) much of that will require help from Jan though. For bios support.
If you figure out how to set the fsb above 66mhz a k6-3+ 500 may even be possible.