Regulations - Yes, Acts of Parliament - very rarely
In in the united-kingdom diagrams are found in regulations, for example legislation dealing with roadside symbols.
There are two kinds of legislation in the UK: Acts of Parliament and Statutory Instruments (normally called Regulations).
The procedure by which an Act of Parliament is passed is that it has to be approved by both Houses of the legislature and then receive Royal Assent (Royal Assent is a formality). The procedure in each House is that the main debates occur at the Committee Stage when amendments are proposed and voted on. At the next stage (Third Reading) the House votes again on whether to approve the Bill in its amended form.
Statutory Instruments (Regulations) are issued by the government (executive) and are known as delegated legislation because the government only has power to issue a regulation if an Act (called the parent Act) gives it power to do so. As you would expect there are safeguards. First of all the courts can declare invalid (ultra vires) any regulation whose terms go outside the limits of the power delegated by the Parent Act.
Sometime the parent Act will provide that Regulations issued by the government under delegated powers become law without further involvement of Parliament but sometimes an Act will provide for some limited further Parliamentary scrutiny. This can be either by the Positive Resolution (the regulation will not become law until Parliament approve it) or by the Negative Resolution procedure (the regulation will become law unless Parliament passes a resolution annulling it).
A key point, in the context of the question, is that neither the Positive nor the Negative Resolution procedure allows Parliament to amend the regulation - Parliament only has a binary choice to approve or disapprove. Of course if they disapprove then the government can issue a new amended regulation which then goes through the same process but the Positive/Negative resolution procedure does not allow Parliament itself to amend any regulation.
I think this explains why diagrams which are sometimes found in regulations are rarely found in Acts. Constitutional proprieties require any Bill to be amendable and any member of the legislature can propose a amendment. If the Bill included diagrams then there would be huge practical problems because any member who wanted to amend a diagram would have to produce his own amended diagram which he might not be able to do/might not have time to do before parliamentary deadlines. So constitutional proprieties would normally mean that in practice Bills must be solely words.
Regulations however cannot be amended by Parliament (see above) so such considerations do not prevent regulations from containing diagrams.
Having said that normally Bills will only contain words, there is this example of an Act which includes a diagram of a symbol. That symbol, however, is defined in an international convention so in practice no parliamentarian would want to amend it.
I know of no examples in the UK where a Bill (as distinct from regulations) contains an image which a member of the legislature might want to propose an amendment to.