A face can't be changed with silent image, but other options exist
Because the spell silent image is in the figment subschool of school of illusion, the spell "cannot make something seem to be something else." An illusion spell of glamer subschool like the spell disguise self, for example, can make a drow's face appear to be a different face, as spells of that subschool can make things "look, feel, taste, smell, or sound like something else."
However, the Disguise skill is usable untrained, and the drow's friends—if he has any—can aid him on the check… or, if a friend is more capable than the drow, the friend can make the Disguise skill check on the drow's behalf, disguising the drow. With enough friends—and the GM's permission—the drow should be able to roam the town unhindered until some high-level watchman with a super-high Perception modifier penetrates the disguise anyway. A disguise created by the Disguise skill has the added advantage of not being magical, so the spell detect magic won't reveal it, the spell dispel magic won't collapse it, and the spell true seeing won't penetrate it.
Also, as a level 5 PC—if this avenue is really important—, the drow could invest 1,800 gp of his 10,500 gp PC wealth in a hat of disguise. Just make sure the command word is utterly mundane so the drow doesn't look like a weirdo when he must reactivate the hat every 10 min.
Finally, confirm with the GM that in the GM's campaign that drow are still feared and hated. In many settings, drow are just different elves, and folks won't, like, kill them on sight or anything.
Yes, they'd get an Opportunity Attack
Your citation on Opportunity attack requiring a 'creature you can see' does imply sight, but that's a much too literal approach to the answer.
A clarification on blindsight and stealth from Jeremy Crawford on Twitter suggests that blindsight allows you to spot a creature - and would thus trigger the opportunity attack. Note: The invisible creature can choose to attempt to Hide - which would prevent the OA.
Blindsight lets you spot an invisible creature in range, but that creature can still try to hide behind something with Stealth.
While ruling in favor of your PCs is a good idea - there may be times when the opposite could occur (a PC with blindsight wanting an OA.) In this case, the blindsight creature knows exactly where the PC is and that they're leaving - which would trigger the Opportunity Attack.
Best Answer
No, except at higher levels.
While there is no specific rule, I would say this is a reasonable interpretation. Creatures with blindsight "can perceive its surroundings without relying on sight, within a specific radius". It seems that most blindsight works on some physical interaction with the object (hearing echoed sound waves for bats, sensing heat for snakes, etc.). Most low-level illusion spells are non-reactive visual and/or auditory illusions, like Minor Illusion and Disguise Self. These spells could not create a illusion that could react to a creature's blindsight in a way that would seem real.
This interpretation seems to be supported by a line in the Blur spell, stating "an attacker is immune to this effect if it doesn't rely on sight, as with blindsight." That said, at higher level, illusion spells can be complex enough to fool certain senses (Major Image) or be able to physically interact with it's surroundings (Phantom Steed).
These are in general cases, of course. Ultimately, it is up to the ruling of the DM whether or not the situation allows the illusion to appear more or less real. For example, maybe you are somewhere where it's really loud and your DM rules that the area is heavily obscured from your bat's blindsight. It would be reasonable to assume that you couldn't sense an object, through echolocation, that you could see visually, so your bat could be fooled by a purely visual illusion (like Disguise Self) in that case. I hope this answers your question.