Would having had a lot of ivs/piccs lead to change in the appearance of veins?

Yes. This may be a sign that the vein has become clogged from the frequent use of ivs in it. Would see your doctor about it.
Yes. . Over time patients that have multiple frequent PICC lines develope narrowing and blockage of the superficial veins of the arms. This process can also involve the larger central veins of the chest. When this occurs the pt often needs angioplasty of the veins to allow access and to promote flow. .
Yes. Having multiple IV or PICC lines will change the appearance of the veins for the worse. Veins tend to develop narrowings, stenosis, occlusions, scar tissue, & even clots within them over time. The longer that an IV or catheter such as a PICC line is in, he higher the chances of these issue. Also multiple lines or IVs over time can cause the same problems. Venogram can determine.